Transmissions (both 4 and 5 speed):
Hints on shifting smoothly (Preloading the shift lever, and WHY)
© Copyright, 2012, R. Fleischer
This very long article begins with a LONG section regarding the 5 speed transmission bearing and circlip problems.
Many folks have problems
understanding, let alone visualizing, how a BMW transmission operates.
I am putting a link at the beginning of this article to help you with that
understanding....and, a second link to help you understand noises and shifting.
Link #1: This shows how a typical transmission, in this case a drum type
cam similar to a Classic K bike, might shift:
www.gadgetjq.com/transmission.htm An Airhead shifts similarly
except that the shift levers are moved by a flat plate cam.
Link #2: This shows BMW GS transmission.
Well worthwhile to review this for information on shifting and various noises,
etc.
http://micapeak.com/bmw-gs/trans.html
Transmission
problems testing:
What are
some simple tests you
can do to determine if your transmission has a problem
developing?
(1) AFTER a
10+ mile ride to THOROUGHLY warm up the engine and
transmission, jack
or otherwise
block the rear wheel so it is slightly off the ground. With
engine off, in neutral, spin
the rear wheel
by hand as fast as you can and listen to the gearbox. This spins
the output shaft
bearings
only. The transmission should not be make bearing
noises when the rear wheel is
spinning.
(2) Start the engine (this is with hot
engine and transmission) and let it idle in neutral. Pull the
clutch in for a few seconds and then let it out. When
the clutch then engages, this spins the input
shaft and cluster shaft bearings only. There should not be a
bunch of bearing noise when you
let
the clutch out (you may hear some normal clutch spline chatter).
(3) Engine off, transmission in neutral, rotate the rear wheel forward
SLOWLY. This is best
done
with transmission hot from riding. ZERO roughness and NO
notchiness must be felt.
After that is done, I do recommend you go further, and that is to unbolt the driveshaft from the
output flange of the transmission and rotate that flange with
fingers. ANY notchiness is cause for the
transmission to be overhauled. Now do a second test, best
done with bolts in the flange, try to move the flange
inwards and outwards. ANY free play is likely caused by
internal PROBLEMS.
These are important tests, as usually a problem shows up with
these tests,
even if
there is nothing much on the magnetic drain plug.
The transmission
output flange has 4 special bolts, and they are NOT
to be used with any type of lockwasher,
contrary to what you may
be told. The thread length of
the latest PROPER bolts are slightly shorter, as the old
split
lockwasher and longer bolts should be eliminated.
There is information on this website about that: Drvshtboltstoolstorque
I suggest you read that
article. The threads should be cleaned, and then a
bit of Loctite BLUE applied, and tighten to 29 foot
pounds. There are various methods of enabling use of a
torque wrench here. You can just give the bolts a
good
grunt with a 12 point wrench; or, torque them properly.
See ALSO my TOOLS article on this
website.
(4)
Inspect the transmission drain plug,
which has a magnetic center. If the transmission is
quite
COLD when this is done, and you are quick about it or have three
hands and extra fingers to
plug the hole, you can loose hardly a tablespoon of oil
(otherwise, drain and collect it).
Inspect the drain plug. A modest amount of FUZZ,
soft-feeling, is fine.
ANY feelable sharp
particles are cause for further inspection. NOTE that
fairly large amounts of FUZZ, soft-feeling,
after maybe only a few thousand miles since an oil change (and
fuzz removal), CAN indicate
that the transmission is failing....and for the circlip-less
versions, indicate that the 5th gear bearing is
deteriorating, and the transmission really should be overhauled
and the circlip installed.
These tests are not necessarily 100% conclusive, and later in
this article are some other tests, so
do NOT stop reading HERE!
What are some common things that are not
usually a transmission failing problem?
(1) Small amounts of 'fuzz' on the
magnetic drain plug, perhaps seen at every 20K-30K gear oil
change. The fuzz will NOT
have sharp particles.
(2) Rattling noise from gearbox in neutral after
thorough warm-up.
(3) Shifting problems, especially from 2nd gear
downward: clutch/input splines need lubrication
(unplated early shafts tend to
need cleaning and lubrication at 15,000 mile intervals, nickel
plated shafts at maybe 25K).
(4) Shifts not always made. Check the
screw in the shift arm...they are known to loosen. Use
Loctite BLUE.
The
"circlip":
The Circlip problem applies to ONLY some
5 speed transmissions!
OVERVIEW of the circlip
problem:
From sometime towards the end (??) of the 1984
production year (no longer do I think this began at the beginning of the 1985
production
year), BMW's
transmission maker made a modification to the transmission.
On the output shaft, they left out a snap ring
(circlip) and shortly thereafter
(?) they left off the
associated output shaft groove (I have reports of at least 3 transmissions from
the
1984 model year that had the grooved shaft but NO circlip....so keep THAT in
mind!)...located at the nose end.
The part number
for the shaft was not changed. That
modification can and did give a lot of grief to owners.
About a decade later the design reverted
back to the original
reliable version. A number of these
'circlipless' transmissions have failed, some have had
catastrophic failures,
ripping the transmission to pieces.
Here
is a link to Anton's website, with photos, and some text, on the circlipless
transmission problems...
you may find it enlightening!
http://www.largiader.com/articles/circlip/
That is only one of two articles on his website you will find of
interest.
http://www.largiader.com/
is Anton's HomePage.
Anton has two articles to look at, not overly clearly shown as
two different links, at least not in MY browser:
Look on the left side, and find 'transmission, clutch, final
drive'. Put your mouse pointer over "transmission" in
"Airhead transmissions and circlip problem". The word
'transmission' will be seen to be a link to his article. Click on
the word.
When finished looking at that article, go back to Anton's HomePage and this time put the mouse pointer over "circlip
problem" and click,
for the other article.
There is not 100% agreement, only maybe 98% (?), on the exact mode
(or reason) for the relatively common
failure of later circlipless
transmissions. There
are two widely differing basic opinions.
Information here comes from a variety of sources. In
particular,
information and food for thought, in real
detail, first appeared in a 2001 Airheads LIST posting by
Bob Clement of BMW-Montana,
who gave me permission at that time
to post his correspondence with me, which I did the majority of on the LIST. In the article you
are reading I have
added further comments from private communications from several
experts in this area, and also my own input.
Thus,
what follows is information from quite a few
sources. This article in its original initial form,
was been submitted and commented upon, and
generally approved, by
transmission experts. This article, well, the circlipless information, has since been updated by ME
a number of
times, and has not been re-submitted, but I believe it to be 100%
accurate.
Many private owners have overhauled their own
transmissions, some seemingly quite successfully, some using
information, tools and parts
from Ed Korn. Most owners will
not want to overhaul a
transmission themselves, and will entrust it to an expert, as
their
are some real
tricks to making a transmission last a long time
and have really smooth operation. Four of the better known
experts are Tom
Cutter
on the East Coast; Orlando Okleshen, better known as OAK
in the Chicago area; Motorwerks (I can't personally recommend
them since I don't
know their workmanship well enough); Ted
Porter (Beemerworks) on the West Coast; Bob
Clement who
does business as BMWMontana; Matt Parkhouse; and Bruno's in
Canada (no personal experience with them, but they have
a good reputation).
At
present, I
am recommending Tom, Ted, Oak, and Bob).
Be SURE to ask how long the work will REALLY take....Oak,
for instance, may have quite a backlog.
Determining if you have one of
the possibly troublesome no-circlip transmissions:
This is not so easy, not so cut and
dried. A factory bulletin in 1986 gave no
specifics on year and transmission serial number. There
was
no change in part number for the output shaft.
THAT is not unusual for BMW, BMW is known to sometimes
make a production
part change and to use the same part
number. It APPEARS that the transmissions that
were affected were shipped with motorcycles of
build date
beginning near the end of 1984, so that means that as early as
some 1984 models may not have the circlip. But,
as I update this
in late September 2008, I have had reported to me ONE 1984 circlipless
transmission...with VIN number perhaps coming soon. TWO
other
1984 transmissions with no circlip but with the same already grooved shaft, were
reported to me by this same overhauler, whom I trust.
Airhead production ceased for
the public in 1995. There was another, later, factory
bulletin, #280, dated 12/08/97, explaining that the
circlip (and,
therefore the groove) was reinstated, and the SHAFT number was
CHANGED. HOWEVER, it appears that the shaft is actually
the same
as the 5 speed output shafts built from 1974 into
1984. The specified 'new' shaft is
23-21-1-338-793. BMW raised the price of
this shaft
tremendously. One can, and competent transmission overhaulers DO, modify the non-circlip shaft, but this needs to
be done very
carefully. The bulletin also
mentioned a 'special bearing' for the front of the output
shaft. There is some controversy about
this, and this
bearing was made by a Japanese bearing manufacturer. More
later herein.
Transmissions beginning with serial 240765
SUPPOSEDLY had
the circlip re-installed. Confusingly, no
year was specified, but
it appears to be mid or late
1995. Further confusion exists... as
year of production and transmission serial number may well not go
hand-in-hand.
I have obtained information on model year versus transmission
serial numbers, and they are presented later in this article.
It
is my belief that you cannot DEPEND on even a 1995 bike as having the circlip,
due to an unknown transmission manufacturing date.
The best information
will be had by looking at the transmission serial number.
Even THAT is sometimes questionable, if you look at the
chart
later on this page.
Summing up:
...it was possible for a transmission built from 1984,
up until
transmission serial number 240765, to not have the circlip
(and the shaft has or has not a groove for that circlip).
BUT:::We have had reports of transmissions AFTER that
# NOT
having
the groove nor the circlip!!...and at least one is listed below.
How
do you find your transmission serial number, and what range of
serials can you expect?? Transmission
serial
numbers are found in one of three places. Early
transmissions, from 1974 to 1981 (or, I believe, as late as 1983,
depending
on country the motorcycle was shipped to), will have
the serial number centered on the top rear center or top front
center, where
you can not see it without removing the air
cleaner, etc. Thereafter, the serial number is
located at the top area of the left side,
just barely below where
the left airbox outlet hose connects; so you have to squat down
to see it. Serials are stamped into the
aluminum
transmission case. There are some variances, and so noted
below.
When reading in this article about 'year', be
advised that BMW's 'model year' includes motorcycles that were
built towards the
end of the prior year, and it is quite possible
to see, for instance, a build date of September, to be included
in the following
year's model. This is due to
BMW policy of closing the plants for the annual holiday
(vacation).
1974: serial numbers ranged from
Y-4300 -> Y20050; after which the numbers continued withOUT
the Y letter.
1975: information sketchy, some end of 1974
transmissions probably used, may have Y prefixes; otherwise no Y.
numbers from 4225 -> 13500 have been identified.
1976: No letter. Probably uses serial numbers
25000 through 51000, some of these may be in 1977 models.
1977: Some from 1976 used, so one can expect serial
numbers from 46000 to 63000
1978: 72400 -> 83000, and THEN had a prefix letter
Z. Some early 1979 transmissions may be that way too.
Z-0870 -> Z-0940. Serials are now on the FRONT inside
face of the casting.
1979: All have Z number, from Z-19100 -> Z-36750
at least.
NOTE 1:
Beginning
in 79 the gusset reinforcements at the bottom of the case were cross hatch like
a crossword puzzle. The 78's
had gusset reinforcement running only from front to
rear. Left to right did not exist.
NOTE 2: BMW
has had fun and games with transmission serial numbers. It is possible
that early transmissions
WITH kickstarters had ZSA serials, for one example.
1980: The Z number now begins with a zero:
Z-052800 -> Z-064950
From 1980, for awhile at least, to 1982, things now get a bit
confused, with serial numbers going to much earlier serials, with
a later year.
1981: There are some numbers that seem to fall in the
1980 group, but the casting is different. Most will find
that the
serial number is now on the left exterior side, as I noted it to
be, just below the left hose of the air cleaner. Expect
serial numbers of Z-006111 -> Z-029900
1982: Z-03660 -> Z-060400
1983: Z-074700 -> Z-084299
1984: Z-084339 -> Z-104600
1985: Z-113701 -> Z-130150
1986: ZSA-125500 ->
Z-125600
Note: BMW seems to be using, at least a fair amount
of time, the letters ZSA for kickstart transmissions.
More information
will be provided to clarify this, in the future, if I can
obtain it.
1987:
1988: Z letter is dropped. From 1988,
serial numbers all now have a 3 letter suffix.
expect numbers from 0147440 AAB -> 0164300AAI.
Suffix's may, however, be AAB, AAI, AAJ, ETC.
1989: 0154140 -> 0176330 and suffix
(note from snowbum: I am SURE that the serials go higher in
the 0176xxx)
1990: 0180939 and suffix
1991: 0190460 -> 0198650, and suffix
1992: 0207050 -> 0215650, and suffix
1993: 0204190 -> 0230075, and suffix
1994: 0237930 -> 0238660, and suffix
1995: 0236539 -> 0254340, and suffix
Some transmissions, by their serial number, may have been put
into motorcycles identified by VIN numbers as from a year out of
the irregular sequence, above. Example:
your bike is a late mfr'd 1991, and has a transmission serial of 0204xxx
plus some 3 character suffix, noted in the 1988+ year, above.
I am collecting information on bikes with KNOWN
circlip-less transmissions....THAT MEANS...known
BY
DISASSEMBLY. Reported to ME circlipless transmissions are:
1984:
ONE, so far: 1984 R80RT....awaiting VIN number and thus the bike manufacturing date.
Transmission is
Z016199. Strange number! Transmission appeared to be original.
It HAD the grooved shaft. NO CIRCLIP.
Well-known transmission overhauler
has seen three total like this. Strange, ...as this serial number would
appear
to be for a much earlier bike.
1985 R80RT, transmission Z113701, VIN
WB1046401F6490338, production 2/1985
1985 R80, transmission Z115902, VIN WB104630XF6480439, production
3/1985
1986 R65, transmission Z127619, ECE (Australian model bike). NO
circlip, NO groove, production 12/85.
1986 R80GS, transmission ZSA124393, VIN WB1034805G6363255,
production 10/85
1986 R65, transmission Z123469,
VIN........................6128105, production 9/1985
1986 R80, transmission Z125576, VIN WB1046303G6480655, production
10/1985
1986 R80GS, transmission # unknown, VIN WB1034801G6363284,
production 10/1985
1986 R80, transmission Z128362, VIN WB104630XG6480782, production
12/1985
1987 R80RT, transmission Z138188, VIN
WB1046407H6491304, production 10/1986
1987 R80 USA, transmission 0144961AAB, VIN
WB1046304H6481119, production 05/1987
1987 R80, transmission 0138910AAB, VIN WB1046301H6481093,
production 11/1986
1988 R100GS, transmission 0151096AAI, VIN WB104780XJ6152090,
production 11/1987
1988 R100GS, transmission 0155023AAI, VIN WB104780XJ6152610,
production 02/1988
1988 R100GS, transmission 0154855AAI, VIN WB1047801J6152611,
production 02/1988
1988 R100GS, transmission 0156870AAI, VIN WB1047803J6152688,
production 03/1988
1988 R100GS, transmission 0155282AAi, VIN WB1047304J6277710, production 02/1988
NO circlip, NO groove
1988 R80 monolever, transmission 0161951AAB, bike serial number
6448037, production 09/1988
1988 R100RS, USA model, transmission 0154894AAB, VIN
WB1046600J6247481, production 02/1988
1988 R100RT, USA model, transmission 0162792AAB, VIN
WB1046907K6293354, production 10/1988
1989 R100GS, transmission 0163629AAI, VIN WB1047809K6153197,
production 10/1988
1989 R100GS, transmission 0164105AAI, VIN WB1047302K6332169, production 11/1988
1989 R100PD, transmission 0171806AA1, VIN WB1047905L6134016,
production 06/1989
1989 R80GS, transmission 0176603AAI, frame serial 6249769,
production 11/89. No circlip, NO groove.
1990 R100RT, transmission 0180939AAB, VIN
WB1046902L6293473, production 04/1990
1991 R100RT, transmission 0185431AAB, VIN WB1046908M6293561,
production 08/1990
1991 R100GS, transmission 01292165AA1, VIN WB1048803M0230223,
production 02/1991
1991 R100R, transmission 0204599 AAI, VIN WB1048707N0280111,
production 10/1991, actually a 1992 model
1992 R100R, transmission 0204181AAI, VIN
WB1048706N0280049, production 10/1991
1992 R100GS,
transmission
, VIN WB1048803N0230711, production 10/1991
1992 (??) R100GSPD, transmission 0207039AAI, VIN not available, can't confirm
production year w/o it.
1992 R100GS/PD, transmission 0209970AA1, VIN WB1048909N0047487,
production 01/1992
1993 R100GS, transmission 022756AA1, VIN
WB1048801P0231259, production 09/1992
1993 R100GS, transmission 0226691AA1, VIN WB1048304P6467330,
production 12/1992
1993 R100GS, transmission 0228652 AAJ, VIN .....646450,
production 01/1993
1994 R100R, transmission 023696AA1, VIN
WB1048709R0280858, production 01/1994
1994 R100R, transmission 238655AA1
1994 R100GS, transmission 0237931AA1, lug stamped NI
1994 R100GS, transmission 0238984AA1, VIN WB1048805R0231610,
production 01/1994
1995 R100 Mystic, transmission 0251758AA1, VIN WB1049706S0400255,
production 09/1995, had no groove, no circlip.
Because of the production date, I removed my comments well above,
about possibly only early 1995 models might
not have the circlip.
More information:
Have the rear wheel slightly off the
ground, transmission in neutral, and rotate the rear wheel slowly.
No notchiness should be felt.
This test can be done with the transmission cold, but is a bit
more revealing if done just after a 10 mile+ ride, so the oil is
hot. This test
tends to also show up a bad
bearing caused by allowing water to get into the transmission,
usually from over-vigorous spraying during
washing (at the hollow
speedometer cable bolt), or from a bad speedometer cable rubber
boot (very common problem, both water
problems can lead to $$$
repairs). This test also tends to show up bad
driveshaft u-joints on the Paralever models, and disconnecting
the U-joint at the transmission output flange, and rotating that
flange, will allow a yes or no on U-joint and
transmission. NOTE!....I highly
recommend making sure
that your speedometer cable boot fits snugly, and is either
internally stuffed with a NON-MELTING grease; or,
BETTER: sealed at the top with
silicone RTV; if the top is poor, water can run down into
the transmission, causing $$$ damage.
Milky
(coffee with cream) look to transmission oil is VERY BAD to have
happen...it destroys bearings.
For the problem under discussion, the
circlip-less transmissions, the most important indication
of a SERIOUS problem that you may
have is sudden VIBRATION....and
possibly noises. If you feel an unusual vibration,
and it need NOT be suddenly extreme at all,
not even very strong
at all, and determine that it is transmission related (pull in
the clutch at a stop, engine running....try in gear and
also in
neutral), that is the time to stop, right
then, and have the bike towed. Failure to comply
will likely, within a few miles, lead to
a massive failure.
I CANNOT EMPHASIZE THIS ENOUGH, FAILURE TO
STOP RIDING, NOW....NOT 50 MILES LATER
AT THE NEAREST DEALERSHIP
OR REPAIR SHOP,,,, CAN COST YOU A BUNCH MORE MONEY.
In fact, if your
transmission is in the range of the circlip-less ones, you might
SERIOUSLY consider an overhaul well before you have a
failure, as
the number of $$ parts to be replaced always greatly
increases as you let the transmission accumulate mileage.
What to do?: Even if you hear and
feel nothing peculiar; every few thousand miles, put the bike on
the centerstand, when the engine
and transmission are thoroughly
warmed up. With engine off, spin the rear wheel and listen
for growly sounds. Turn the wheel slowly
and feel for notchiness. When the engine and transmission have cooled
overnight, check the drain plug. GENERALLY the
degradation is slow, but sometimes it DOES come on
suddenly....noises and/or vibration.
NOTE: BMW, like most manufacturing
companies, is tight-lipped regarding engineering details when it
makes a change.
BMW tends to be more tight-lipped than many
companies, probably from both a corporate policy and the Germanic
'we
don't wrongly engineer ANYthing, WE don't have
problems....'. BMW, Germany, or North America, may
well issue Service
Bulletins of various sorts, now and then, but
these often do NOT spell out details that one might like to have,
and sometimes
are confusing, especially by what is not
said. We have to live with that. Sometimes some
of us Wrenches manage to get
information that is not very public,
to say the least. In in some instances I have been given
information that is almost to be
considered Top Secret. I
can NOT divulge in such circumstances my sources, and can
almost never exactly quote the
information. BUT!!.....one
way or the other, in almost every instance, I DO manage to get
the information needed to you all.
Viewpoints on the circlip 'problem'
#1: This is the more
commonly accepted viewpoint:
It is this viewpoint that I personally agree with.
There are three shafts in the transmission,
INPUT, INTERMEDIATE, and OUTPUT. The front gear teeth
on the output shaft is
manufactured on an angle, that is, the
gear is HELICAL cut. Its mate must also be on
that same angle. If you picture in your
mind
such a gear on a shaft, and another shaft with a mating gear, and
if power is fed to ONE, then the other has forces, such as would
move the gear along the axis of the shaft, not just being
rotated. This direction of axial force reverses, depending
on powering from the engine,
or engine braking. In the 5
speed transmission, even in neutral, the forward gear (5th) gear
on the output shaft is being pushed forward
any time the clutch
is engaged, even in neutral, except in the coasting
condition. A BOSS on the front of that gear pushes against
the
rear face of the inside race of the front output shaft
bearing. That rear face of the inside race of the front
output shaft bearing is the
thrust surface for 5th
gear. Thus, 5th gear is constantly trying to
push against the front bearing. Another
way to look at this, is that
forces try to move the helical 5th gear forward, and move the
shaft backwards, the gear then moving on the shaft. Because
of this, the
front bearing is always damaged, and sometimes the rear bearing,
and even the rear cover plate!
There is a tiny
amount of end to end float in the shafts fitment in the
transmission case (a few thousandths of an inch), established
during
the shimming process, which ensures that the bearings are
not subjected to end-preloading. Ball bearings,
used in this transmission at
that point, do NOT like preloading,
that makes them heat up, and fail.
There ARE some very special
types of ball bearings designed for end loading, these are used
in such as the worm drive shaft on electric
winches, but this is
not pertinent here (and those bearings are VERY
pricey).
Prior to the change in what
I think was late 1984, there was a hardened snap ring,
a CIRCLIP, that fit in a machined groove
on that output shaft, it was just forward of the gear, and
prevented the bearing from moving forward from that mentioned angled
(helical) cut gear pressure. That kept the pressure from eliminating
any decrease in the shimmed float.
When the circlip is left out, the first thing
that happens is that the axial thrust from 5th gear causes the gear to push the
inner race of the output
bearing along the shaft towards the front of the
transmission, as the shaft, in essence, moves rearward and the
gear moves forward on it. If
the bearing race moves far enough, it will
eliminate any end float. This places an axial load on the bearing, that
will cause it to eventually
overheat and fail. The large front bearing overheats,
begins to self-destruct (the cage which keeps the
balls in place starts coming apart and
metal goes all over the place).
More clearance develops, the output shaft can actually wobble in the
bearing. This will, if bad enough, result
in the output flange on the
transmission (driveshaft U-joint flange) contacting the
transmission lip area where the boot is, and the output rear
bearing distorts; and, with metal bits already getting into things, all sorts of mechanical mayhem happens, and rather
fast. From the first
sign of unusual vibration,
things deteriorate rather quickly. If allowed
to proceed, gears, bearings, shift fork, and even the
rear case of the transmission, are ruined.
#2: This is a far less accepted viewpoint:
This point of view is quite different.
I do NOT agree with this view. This
view is that while the helical cut gear does move forward under
load, it presses the inner race of the bearing, and it takes that
load because the outer ring is against the gearbox case....and
thus the circlip
is of no matter. Thus if the clip IS
there, the entire shaft moves forward, and the bearing always
takes the axial load, and no force moves
the inner race relative
to the shaft. This point of view is thus that the
smaller bearing should fail first if preload was a
problem....and....there
are NO circlips on any of the other
shafts....and, further, the purpose of the circlip was to assist
with disassembly! During the heating of the
transmission, the case should release all bearings, but a
circlip-less large bearing COULD remain in the case when the
shafts are removed,
and it is a bit of work to remove the
bearing...that one, as it is larger, sticks in the case recess...
so the clip was used. These folks agree
that
the clip removal coincided with the increased bearing
failures....but say that the increased failures are NOT caused by
the clip removal,
it was coincidental with the Paralever
introduction. They say that the GS Paralever
introduction, with its extra travel, puts forward thrust
into the
gearbox, and even an angular thrust due to the changed design
(dual travel angles of the Paralever), and that said angular
thrust is
taken up by that large 6403 bearing.....and 'proof' is
that no extra large REAR bearing was installed by the
manufacturer. Thus, these folks
believe
EXTERNAL forces are the cause for the gearbox failures, and they
tend to blame too high spring preloads and poor lubrication on
the splines. They feel that BMW put the circlip
method back into production as it was cheap to do, and shows that
BMW 'did something'.
MY viewpoint: The above #2 viewpoint is faulty.
Circlip-less gearboxes on NON-Paralever have certainly failed in
this area....negating the
above arguments. ALSO, I know of
NO failures of any gearboxes in the fashion mentioned in this
article that were not fixed permanently by
modifying the shaft and installing the circlip (with new
bearings, etc....as required). So...I just can't buy
that argument; especially when
considering the thrust given by helical gears..
Note: It has been reported to me that the
stock Paralever driveshaft has exactly the same pivoting length
as the swing-arm, assuming the
rubber damper is OK, and as long
as that is intact, there are no axial forces on the output
shaft. Another reason for negating some of argument #2.
<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>
NOTE regarding that previously mentioned 'special
6403-C3 bearing' for the front of the output shaft: It
appears similar to any other
6403-C3 bearing, but the front face
of the inner race (forward edge of the inner race, the side of
the bearing which has writing on it) is cut with
a 90° angle
(much smaller taper to it than the rear face of the inner race)
between the face and the inner hole where the bearing slides over
the output shaft instead of the 6403-C3 bearing which has a
tapered angle. The forward taper is almost
absent. Perhaps this was done to
minimize the
possibility of bearing creep as the bearing is pushed against the
retaining circlip by 5th gear. This modification may well
have
never been needed. The regular bearing worked fine,
never a problem with bearing creep leading to bearing axial
overloading....UNTIL
BMW started leaving out the bearing
retaining clip. This new bearing MAY be the accepted
choice....but: The more commonly accepted
view is that the
elimination of this cheap clip and associated groove caused the
problems...AND...the last word I had was that if one now
orders
the 'special bearing', you get a STANDARD 6404-C3, withOUT the
modified inner race face. The 'special bearing' was used
only for awhile, and BMW went back to the regular old bearing???
Generally speaking, modifying the shaft,
installing the clip, new bearings, seals, re-shimming, etc., will
be very favorably
priced, compared to just a new shaft from
BMW! Those doing their own overhauls can
have a good machinist cut the
groove to accept the snap
ring. Re-shimming is, of course, necessary with new
bearings, etc.
<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>
Here is an EDITED (by me) query and reply, as
was on the Airheads LIST in November 2004, that will explain
about one
little thing you might otherwise overlook, if you are
overhauling your own transmission:
The transmission was a 1983 or 1984 R100RS.
The owner decided to do an overhaul ...it had been done
previously, probably by him,
and the mileage was now around
200,000 km. He noticed a small
"rumble" or notchiness in the output when revolving
the output flange,
the driveshaft shaft disconnected. No
sound, no notchiness when tested from the wheel with the
driveshaft connected. A transmission oil
change (done every
6 months!) showed normal metal powder on the drain plug
magnet.
Transmission was removed and he slightly released the gearbox
cover screws (1-2 turns) and the notchy feeling disappeared
totally. Sounds
like a preload problem??
The owner then measured the clearance between the output shaft
snap ring and the big bearing (6403) inner
race; the inner
race pushed as far as it goes down the shaft. A 0.25
mm feeler gauge was a bit tight but a 0.20 mm loose. So, he
concluded
that there must be more than 0.20 mm
"undefined" clearance in the shaft and it seemed to him
that there is no reasonable way to shim the
shaft within
0.1 mm as required especially if the bearing may drift along the
shaft. The owner then felt that he would have to shim the snap
ring and the bearing inner race to zero clearance.
The owner continued....(my editing here): My actual question is
about the "bearing drifting along the shaft due to missing
snap ring" theory:
If the front bearing inner race
moves along the shaft (despite press fit) ...what... is holding
the shaft in place ...that the drift can take place?
If it is the smaller bearing then the snap ring push will really
prevent big bearing drift but this may cause a situation where
the shaft drifts
in the smaller bearing, not the big one.
Again, a preload will result. He also wanted to know what
happens to the bearing outer races
in operating temperatures? Do
they float ie. are they free to move away from their
assembled positions? The operating temperature is not
very far from the assembly temperature where the bearings
practically can be dropped in their places.
Tom Cutter replied: There are several forces at work that
can dislodge the bearing inner race from the shaft. One is the
weight and forces
of the driveshaft as it undergoes normal
rotation, the forces placed upon the output shaft are
cyclical, both rotationally and axially. The
bearing
is designed to be captivated by the clip to preclude ANY axial
movement of the bearing race upon the shaft.
Unfortunately, the
bearing now sold for the output shaft
is dimensionally slightly different from the one designed
for in the original plan. That bearing had a
square
corner on the rear face of the inner race, so that it would press
evenly upon the circlip. BMW only offered that bearing for a
relatively
short period, then they substituted a standard
6403 C3 bearing in its place in the parts system. The
standard 6403 bearing has a VERY
generous radius on the
inner bore, which makes the race bear on the very outer
edge of the circlip. In some cases the clip becomes
dislodged into the adjacent void. The problem is exactly as
you have mentioned, and is the cause of the premature failure of
so many
gearboxes. The cure is to shim the inner race so
that there is no possibility that the bearing can be
displaced. This can be done with
flat shims, although BMW do not
offer such, or by simply fitting the
round wire expansion ring that BMW used for the
purpose.
(Emphasis
in red by me, Snowbum)
This round wire expansion ring
sits down in the radius of the bearing bore, and effectively
fills the void so
that there is metal-to-metal contact from
bearing to circlip (snap ring). The circlip is:
07-11-9-934-100
(size 17 x 1). This is the same circlip
used on the shift shackle in the transmission, in case you get
curious
about it.
The round wire expansion ring
is 23-21-1-235-006. BMW uses the term Expansion Ring for the wire
spacer at the
bearing under discussion, and the word circlip or snap ring is
the part that goes into the shaft groove.
The output shaft 0.040" (1.01 mm) groove is
0.5 mm deep,
located at 17.00 mm from the step on the forward
end of the shaft
where the 6403 ball bearing sits. Machining should be by
1.00 mm carbide tool. Be sure to
check your shaft, and these
numbers, don't trust ME here that YOUR shaft is the same. The groove must be
VERY precisely located so
that the round wire expansion ring, mentioned above, CAN be
installed. The
inner race of the bearing we
have been
discussing must be installed so it presses (well, touches) on the circlip.
It should not
be installed towards the rear
(maximum space between inner race and circlip).
MY feeling is that
if things are done precisely, then the expansion ring must be installed.
However....I have mixed feelings on that.
NOTE: The circlip groove is, by eyeball, rather close to the end of
the shaft. I have not given specifications for the groove
from the end of the shaft as that is NOT the measurement that is critical.
I,
UNfortunately, never took any of my own photos when doing the circlip machining
job. However, here is a link to an article with
photos. I agree with the article, for the most part, with
some hesitancy about BMW not using the round wire
expansion ring
at times. The article will show you what the shaft
looks like, the groove being cut, etc.
http://www.gunsmoke.com/motorcycling/r100gs/tranny_circlip/index.html
Here is another
article with photos. Be sure to look at this
one.
http://www.largiader.com/articles/circlip/
http://www.largiader.com/
is Anton's HomePage.
Anton has two articles to look at, not overly clearly shown as
two different links, at least not in MY browser:
Look on the left side, and find 'transmission, clutch, final
drive'. Put your mouse pointer over "transmission" in
"Airhead transmissions and circlip problem". The word
'transmission' will be seen to be a link to his article. Click on
the word.
When finished looking at that article, go back to Anton's HomePage and this time put the mouse pointer over "circlip
problem" and click,
for the other article.
One thing to really think about
is what to do if you think you have a transmission
withOUT the
circlip. Whilst I am attempting to identify the full range
of serial
numbers, year, model, etc., that for sure have no circlips, it still remains a bit
wishy-washy, although less so as time goes on. You do
have a choice on what to
do, or not to do.
If you intend to go through the transmission
yourself, you may be opening a can of worms. If you send it to a
specialist, you will want to contact one
of our transmission experts, as there is a LOT to know. You
could send it as a preventative measure. If things come
apart in the transmission, metal will go throughout, and cause a
LOT of damage, typically.
The one's I tend to trust are:
Ted Porter at Beemershop, Scott's Valley, California
service@beemershop.com or
tedporter@beemershop.com
Bob Clement in Roberts, Montana
bmwmontana@aol.com
Matt Parkhouse in Colorado Springs
hobomatt@aol.com or
bmwhobo@gmail.com
Oak in Chicago area.
askoak@aol.com Be sure to ask how long the work will
take, he may be very backlogged.
Anton Largiader in Charlottesville, Virginia
anton@largiader.com
http://www.largiader.com/
is Anton's HomePage.
Anton has two articles to look at, not overly clearly shown as
two different links, at least not in MY browser:
Look on the left side, and find 'transmission, clutch, final
drive'. Put your mouse pointer over "transmission" in
"Airhead transmissions and circlip problem". The word
'transmission' will be seen to be a link to his article. Click on
the word.
When finished looking at that article, go back to Anton's HomePage and this time put the mouse pointer over "circlip
problem" and click,
for the other article.
Tom Cutter in Yardley, Pennsylvania
tpcutter@aol.com
You could also take the attitude that you will
watch things carefully, and at
the first sign of problems with
your OFTEN inspected magnet that is part of the
stock drain plug (and,
disconnecting driveshaft and rotating the output flange
as noted in #5, way
above)....you will pull the transmission and have it modified and
overhauled. You would also carefully be watching for sudden
vibration....and
have promised yourself to stop right then....not
proceed another few miles....
It is up to YOU!!
***Special note on the throwout
bearing area. This is being put into this transmission article
(it is
expanded upon in the CLUTCH article) due to the
potential for someone to think that the transmission
has a problem...which, in
essence, it does, since the throwout bearing is LOCATED in the rear of the
transmission.
Typically, the clutch will start to slip, when the transmission gets fully
warmed from riding.
Some tolerances on some transmissions throwout area bore
sizes, and throwout pistons, were not held tight (well,
LOOSE) enough. Generally this
is thought of as from
1981, when BMW changed the clutch design
radically. If the piston fits into the bore a
bit too tightly...it may still operate
smooth enough, but under
some circumstances (temperature, as in HOT!) may
stick. Measure the piston, and if it is over about
1.13" (28.7 mm),
you MAY want to reduce the outside diameter
a bit. I have seen these as large as about 1.142" that
still worked OK. I can't give a hard and
fast rule here,
but if yours is up to 1.141 or so, I would certainly see how it
fits, and if a bit too much friction, I would recommend sanding
the OD a bit. The pressure on them in operation is rather
square, so if any doubt, ....if careful... you can chuck the
rather short shaft tip end
in a drill press and use some rather
fine sandpaper for this. Inspect the bearing, and if it
looks bad, replace it. Grease it with a good LIGHT
grease
(NO moly). The reason to use light grease is that it takes time
and miles for the transmission OIL to reach this throwout
bearing. Oil
the outside of the piston as you
assemble this area. Clean and lubricate the arm and
associated parts. BMW has a replacement piston:
23-13-1-464-167 which is pricey as it includes the bearing and is
a new design, that eliminates the clearance problem of the old
style
piston...but you do NOT need to purchase it, unless you
cannot find a new old-style bearing (if YOUR bearing is NG), or,
you don't
wish to sand YOUR old piston (if required).
NOTE that the original piston is not a
one-piece metal part, rather, it is a part-plastic item, and it expands
much faster than
even the surrounding aluminum alloy, so common
'feel' for clearances may end up leaving it too
tight. The updated part fits
directly, no
problems.....you measure and decide. I sometimes test the fit
with the transmission at operating temperature.
NOTE!!....There is much more extensive
information on the clutch throwout lever, the bearing, etc....be
SURE to see it on this website!
clutch.htm
That article has a photo of the later style clutch
throwout parts, and the actuating rod, and notes on the FELT on
the
pre-1981 rods, ETC.
NOTE: From 1970-1980,
the 4 speed transmission had a ball bearing throwout bearing; the 5 speed
transmission had a radial needle bearing type.
From
1981, BMW made only the 5 speed transmission, and BMW went back to the superior
ball bearing.
NOTE: The 4 speed transmission and the early 5 speed transmission
(pre-1981) clutch push rods had felts located in a groove, and are installed
best
from the front. The 1981+ transmissions did not use a felt, and had a SEAL
instead, and the rod CAN be installed from the rear.
See the NEUTRAL
SWITCH article on how to replace a neutral switch on a 5 speed
transmission: Neutral
Switch replacement.
Replacing the input shaft seal:
This can be relatively
easy, or can be difficult. Usually when the seal leaks, the
transmission is about ready for an overhaul. Let's assume
that is not the case.
If the seal
leaks, oil from the transmission can flow along the splined input
shaft into the clutch, oiling the clutch, and then it will slip.
When you have the
transmission either out (or backwards some), to
do the normal scheduled input spline cleaning and re-greasing,
put your #1 eyeball on the transmission
input seal. If
leaking, remove the transmission to the workbench. It is
important to not score/damage the input shaft when removing
the
seal.
You can make a tool to try to remove the seal.
HEATING the area with a moderately broad flame of a gas
torch will help. If the seal is not
going to come out,
the next step is to drill quite a few holes into the seal, the
holes should be perhaps with a 1/32" drill bit.
Drill the holes as close as
ou can around at the outer diameter
of the seal, but DO NOT drill into the aluminum of the
transmission case that is surrounding the seal's outside
diameter.
I suggest
you use a shop vacuum to get all the drilled metal pieces into
the vacuum cleaner, not the transmission. Remove the center
of the seal and then
try to remove the outer part.
If this does not work, you will have to
remove the front cover of the transmission to press out the seal.
Once
the seal is out, use a strong solvent and if needed clean up
the mounting area very carefully, using fine grit sandpaper if
you have to, and
use that vacuum cleaner. When
replacing the seal, oil or grease it, otherwise you may dislodge
the coiled spring in the seal. Use some
sort of tool
such as a socket or big washer, so the seal goes in squarely.
NOTE
that excessive end play
of the transmission input shaft can
cause a quite-grabby
clutch operation, and
that can happen cold and/or hot, but more
often when hot. To fix THAT, one must remove and open the
transmission and work on the shaft shimming. One can get an
idea if that is a problem by removing the
transmission, heating
it to about the temperature of boiling water, and measuring, with
a dial indicator, the
input shaft end play. Anything over a
few thousandths of an inch is suspect. I'd not want over maybe 0.005" This problem with
transmissions
causing a grabby clutch is not overly common, but
it seems to be more so for the 1979 models. Another
cause is excessive end-play on the crankshaft...rare.....about .007" is the
maximum I personally would allow, and that is for a DRY assembly, which means
you cannot take a measurement that means much, when oil is in the end parts!
All the rest of the Transmission "stuff":
Sometimes I am
asked about the various years of transmissions as to good points,
bad points, etc. A lot of information
is in the
article you are reading. However, the 1974
transmission is a special instance. This was a
transition year for
BMW, from the /5 to the /6, and there were
some things not so nice about the 1974 transmission. 1974
was the first
year for the 5 speed box. The Pawl springs
tended to break. The kickstart parts were SOFT...and use of
the kickstarter
is NOT recommended. There were problems in
positively locating the Neutral position, and that wasn't fixed
until 1976.
The 1974 transmissions, in other words, did not
hold up well. Some parts are no longer
available. This parts problem extends
into
the 17.5 and 15 degree parts area (you might find some parts not
available that are needed to match your 15 degree
parts; so you'd
have to convert to 17.5 degree parts)...... AND, when you
see the parts prices, you will scream. If a
1974
transmission is really bad, YOU REALLY MIGHT WANT TO
CONSIDER A NEW TRANSMISSION; or, preferably, a
really expert rebuilt
one (especially one after 1974 modelS)...as the price is less, and the quality will be...or
can be.... BETTER
than a brand-new
one! Quite often, the best thing to do with a really
bad 1974 transmission is to obtain a later model;
those up to
1980 will install with no problems.
The transmission experts I tend to trust are shown
near the end of this long article.
1981 was also a bad year for transmissions. So was 1974.
Here's some more information:
1. see:
http://www.largiader.com/tech/airtrans/
That article has a number of photos and descriptions that
you may find very useful in understanding the 4 and 5 speed
transmissions in a few areas, such as the
input gear that has the shock absorber cam ears that sometimes
breaks on the early 17.5° transmissions (1979-1982);
information on the shifting
mechanism and 'shift kit', and some other things. I highly
recommend you review that article....and the links at the bottom.
Note that 17.5° gears were supposedly installed from 1982, and I am not at all
sure that is correct.
CONTRARY to what Anton
says about my article, that you are reading, I cover a huge
amount more than just 'historical' data.
I suspect Anton looked at my article, and did not scan down very
far. I also get into a lot more depth on things, including
the
input cam-gear ears, etc.
AND...regarding that input gear: see #3, just a bit below
here...for a more vigorous treatment of the input cam gear and
the 17.5° transmission, ETC.
2. NOTE!!! see article: oiltransfers.htm
The output shaft oil seal on all models except the Paralever,
have the open side facing
rearward. The Paralever output
shaft oil seal open side faces INward.
A new style seal is being used on the
Paralevers, install dry, shaped for a couple hours on some sort
of mandrel, and then being very
careful about the installation, to avoid
the seal being damaged by the speedometer drive. You can
use some tape over the drive gear
to avoid damaging the
seal. If you have an early model of the Paralever, there
may be a goodly sized V-vent at 12 O'Clock in the
housing.
Block this vent and drill it 1mm. Later models have this
already modified. Wet driveshaft models used a green
seal.
If you have a non-Paralever model, and oil is transferring from driveshaft to
transmission, you have one or more of: too high driveshaft
oil level; sacked suspension; extreme downhill riding; ....and
may want to fill the 12:00 notch....be sure to leave it with a teeny hole in the
filling. You MUST have a hole. See #4 just below!!
3. The input gear on the 5 speed transmissions has
been changed FOUR times, used with THREE different gearsets.
The original input
gear was 23-21-1-231-519, often just called the -519 gear.
This was used from 1974 to sometime in 1982. The 1979 to
1982 ones
have been known to CRACK. Actually, some from a bit later
also have cracked.
For the helical, cluster, and 5th gear, BMW changed, for
all by mid-1982 or so, from what is often called
the
Gear Angle, from 15° to 17-1/2°. The fiche may show earlier in 1982. The actual changed angle
is not exactly the part of the gear appearance you might think;
rather, it was
the tooth profile. Because of this change, the -519
gear also had to be changed. BMW did so, and still had problems
with it...so they did
another change, beefing it up. They had to change the
input SHAFT too. This occurred in 04/1982, and continued
until other changes,
in 02/1985. The new shaft for the 17.5° gears was
23-21-2-302-331 for NO kickstarter; and -332 for WITH
kickstarter. The shaft was
shipped complete, except for rear bearing.
Further explanation: Some 1981 bikes had the first changed
17.5° gear on the input shaft....this was the small shaft, with a
COARSE spline.
The 1981-2 change was to a FINER spline...and then even later to
a larger diameter gear set!
All this being
said, still, the generation of
17.5° input gears, from 04/1982 to 02/1985, might break ears.
This is when BMW added splines to the drive dog that mates with
the
input gear. This change occurred with transmission serial
number 115167 on 03/1985 (I think).
Here some of the information is presented a bit
differently, for clarity:
In April of 1982 (from serial 58225 on the
transmission??) the helical-cut gears in the transmission were
changed from 15° to 17.5°. The
new 17.5° gears are
identified by a cross or star or X marking on one
end. They are NOT interchangeable with the older 15°
ones, and
only 17.5° matching gearsets can be used. Supposedly
BMW also identified these updated transmissions with blue paint
dot on the airfilter
housing surface of the transmission.
However, the later transmissions do have serial numbers on the
outside, check for yours under the air
cleaner box on left OUTside. From 115167 (from April 1985?) the input
shaft assembly was redesigned. The earlier gear had a
smaller
ID, and fit the smaller input shaft OD...with short
splines. The reason for the second generation update was
because the first generation of
the 17.5° input shaft gears
(4/82>4/85) were weak and the drive ears might
break. These updated parts can be fitted to an
earlier gearbox
with the 17.5° gears. The original fragile
input gear is probably still available from BMW. However, the best
thing is to install the complete
second generation input shaft
assembly. The part is 23-21-2-302-331 if you have no kickstart gear; and 23-21-2-302-332 if you do have
the kickstart
gear. Supposedly these transmissions are identified by a black painted
panel in the ribs in the aircleaner mounting area. Note
that in one other respect the input shaft used on the 1981+
models is not the same as the older gearboxes, due to the
redesign of the
clutch, etc., the earlier ones have a longer nose, see #8 below.
Thus there were at least two changes to
the input shaft.
MORE!
It has become apparent to me that some
of you do not understand certain things about the 15 to 17.5 degree change by
BMW, maybe you have never had
a transmission apart, or maybe, for whatever reason, it is still confusing.
I will try to explain it a bit differently here...and add a bit more too.
You must be very
careful when changing parts to not mix the wrong gears, and this can easily
happen with the bevel-cut 5th gear on the output shaft...yes, the one that can
have the
circlip area problem. You already know that the 17.5° gear has an X
mark on it. What may not be clear to you, is that if you need a new
intermediate shaft, or have
access to the large 20ton+ type of press needed to disassemble that shaft-set,
updating the gear on the intermediate shaft means you MUST change the output
shaft
bevel gear to the later 17.5° type. .....AND, must change the -519 gear on
the input shaft. BTW...BMW does not sell the intermediate
shaft except as an assembly
and it is very pricey; which is why some use old gearboxes for parts!
Early versions of the intermediate shaft are NLA from BMW!
Because of the possibility of you using wrong parts, it is best to inquire on the Airheads LIST if you are at all confused!
4. Only the 1970 and 1971 transmissions did NOT have the
tiny notch for breathing, at the transmission output seal 12:00
position. (yes, the Paralever boxes
have the notch sealed).
Because of that, the driveshafts on the 1970-1971
bikes tend to have their 'rubber' bellows swell up in hot weather
riding. This slight
pressurization can also cause oil
transfer problems. An article was written about this,
and is in the September 1981 BMW News.
The only GOOD cure
is to add the transmission output vent...a drilled hole or
hand-filed hole will do. Other forms of venting, even
modifying the driveshaft oil plug, etc., do NOT work well (even
with a several inch long line run upwards). The shaft
housing could be
vented in the more forward area, but the BEST
fix, if you have to fix this problem, is to put a vent in the transmission output area, as in later airheads.
5. There are quite a few 'tricks' and adjustments that
don't readily appear to someone taking apart a gearbox. For
a truly good operating
gearbox, you WILL want to consider a specialist.
6A. The 1974 transmissions had a soft kickstart gear on the
input shaft, which can cause problems. It is best to not
use the kickstarter,
except in an emergency. A
replacement part will be hardened.
6B. LOTS of changes were made to the
transmissions over the years. Sometimes the serial numbers of the
transmissions, or bike serial number, were not\
well identified as to when changes were made. It can get very complicated,
one of the reasons I recommend transmission specialists. Some
examples
here would include the shifter fork groove on the sliding gears that changed
from 6.5 mm to 5.7 mm; square undercut dogs (and associated 'windows') for
3rd, 4th, and 5th gears; the detent spring change on the selector bracket; the
casting was changed for a stronger selector fork shaft, old was 100 mm, new was
105 mm. BMW changed the shifting parts numerous times. They
did NOT incorporate all the changes at the same time. The OFFSET segment
for pawl
spring clearance was one such change. Several changes occurred at that
same time, with transmission Z5A79720.
.......and there are DOZENS of these sorts of 'nice to know, or NEEDED to know' items.
6C. The /6 kickstarters are not really meant
to be used a lot. The 1974 was weak (see 6A.). NEVER
just jump on the kickstart lever.
Be SURE it is properly
engaged. MY method is to use light foot pressure, until the
lever seems to engage, then use the clutch lever at the
bars to
allow the kickstart lever to move downward an additional small amount. This ensures proper engagement.
Release the
clutch lever. KICK.
NOTE!! The kickstarter lever on /5
and later will 'bottom' on the footrest rubber. It is
important that it not be a
pure metal contact.....
and on the /2 bikes, there is a rubber
bumper. The rubber must be intact.
7. The improved shifting setup, with the external linkage
mounted off the footrest is probably still available as a kit,
for the earlier 5 speed
transmissions. The design change
occurred in 1978.
8. In 1981 BMW made changes in the transmission clutch
throwout bearing area, internally as well as the external shift
lever arrangement.
Also in 1981, BMW made a large change to
the clutch and flywheel, which became a totally different design,
and the flywheel is now called
a Clutch Carrier....and the
transmission input shaft was changed (shorter) to accommodate those changes. Transmissions before
and after
that date can be interchanged if the input shaft is the
correct one.
The input shaft is about 24 mm long on the early
transmissions, and from 1981, it is about 19 mm long.
It is also possible to
shorten the input shaft on an early transmission, in order to fit
it to a later clutch unit...by simply using a
cutoff disc, etc.,
even with the transmission still together! Be
sure to radius the forward edge properly.
Within certain guidelines, such as the input
shaft length, and internal gears angle cuts, shift kit or not,
proper neutral switch...
etc...as all mentioned in this page, most all
the transmissions generally interchange.
9. Shift
kit and pawl spring, etc:
Pawl Spring:
Inside your transmission is a detent spring, that enables the
shifting mechanism to shift gears.
If that spring breaks,
....you are stuck in whatever
gear you
happen to be in. You MIGHT be able to remove the fuel
tank, turn the bike
upside down, and then shift into a
gear...maybe. I've heard
of this, never done it
myself. All the 5 speed transmissions up to the early
1980's could have this spring breakage defect.
This particular spring
is used in all years all transmissions. Pawl spring breakage fix:
One can turn down the boss it rides on by about .060". The boss
needs to be
around 0.613" or below. If yours is about .630, then machine it down.
Tom Cutter posted to the Airheads list that the original was 15.95-16.0 mm;
and the change should be to 15.55-15.6. I don't hold to such
tolerances. Here is my take on the matter:
The post the
spring is on has had its diameter changed in the 'shift
kits'. You can certainly
reduce the diameter of the stock
type. The spring must
not bind-up in its operation. Certain of the so-called 'shift-kit' parts, Pawl 23-31-1-242-892; and
Segment (offset link) 23-31-1-231-578,
supposedly will 'cure' broken pawl
spring problems....but modifications work well. The shift kit
uses spring 23-31-1-242-910, and you
must use that
spring with the shift kit. This is the straight
legged spring, as opposed to the original type 23-31-1-231-619
which was bent....and
is no longer listed nor available.
Shift Kit:
In mid-1982 (could be during the 1981
production year, this is unclear to me) BMW installed a so-called
'shift kit' inside the transmission....
this is a fairly
extensive kit with a revised cam shape, modified shifter arm,
etc. It is retrofitable, and can be considered for
earlier
transmissions when overhauled. BMW has a habit of phasing in changes,
sometimes on some models long before others....and
on occasion one might find a far
later serial number withOUT the
shift kit change; and transmissions with partial changes. But, that
said, the 1984+ transmissions had the transmission serial
number
on the left outside, just under the airbox fitting surface, at
the air tube to the left carburetor area. The earlier
transmissions had the
serial number at either the rear top, or
front top, but you must pull the airbox to see the number.
You will do that at the spline service anyway.
The serial number for the beginning of the shift kit installation
is: 56477 (if one can believe that)...that means FROM 56476.
The prefix was Z or ZSA.
The purpose of the shift kit was to
eliminate false neutrals or hung-up shifting, and improve
shifting in several ways. The kit is part number
23-31-9-056-150. Later transmissions incorporated these
parts.
The kit as such is no longer available, but the parts ARE.
Note as mentioned earlier that numerous parts changes in the shift mechanism
occurred over a number of years....such as the offset segments and pawl spring
changes.
In the September 2003 issue of BMW Owners News, from
page 34, is an ILLUSTRATED article on replacing a broken
Pawl
Spring in the transmission. Just a couple of comments by
me: In illustration 15, the torque obviously should not be
24 foot pounds.....5 to 6 footpounds is correct. In the
article, the author does not mention that the BOSS needs to be
relieved
to be sure the spring does not bind up and break,
again! See way above in this long transmission article of mine that you
are
reading...about that boss and spring.
In the November 2003 issue of BMW Owners News, from page
34, is an article on installing the updated shift kit.
There
are some errors in this article:
a. In the first column of page 34,
second paragraph, the kit does NOT NECESSARILY allow shifting
with a broken spring.
b. On page 34, photo #1 text, it is NOT
true that there are no differences. There IS a design
change. The 1974 and 1975
had a reverse neutral....that
is....the plate PROTRUDED at neutral, rather than being DETENTED.
The new design
makes finding neutral much more distinct and
positive. The Neutral switch was changed, and
although they look similar,
they are not. The newer
plate shaft is changed to insure against clashing with the pawl
arm. Photo #3 text should not
really have the second
sentence worded like that.
c. On page 35, photo #4 text, it is NOT
true that there are no differences. The new arm has an
offset to avoid binding.
NOTE!!!....The "shift kit" is most effective on the
1981 and 1982 models (to maybe
1983, depends on exactly when BMW
phased in the
shift kit themselves, on the various
models),
because these have the lightened Flywheel, called a Clutch
Carrier.
The shift kit might
improve earlier
transmissions slightly, and maybe slightly even
more IF the early
heavy flywheels have been considerably lightened.
The
shift kit does much less for those with the heavy
flywheels.
The shift kit did NOT come with any
instructions.
BE SURE that in your assembly of shift kit parts that the arm is doglegged, that is, off-set.
The shift kit is made up of the following, still
available parts:
23-31-1-231-578 segment shaft (offset link)
23-31-1-231-611 shifting cam (for 1-2, 5)
23-31-1-242-892 pawl
23-31-1-242-910 spring
23-31-1-451-563 shifting cam (for 3-4)
***The so-called
shift-kit parts, Pawl 23-31-1-242-892; and Segment
23-31-1-231-578, supposedly will 'cure'
broken pawl spring
problems....but modifications to the stock boss and/or use of the upgraded
spring work
well for that particular problem,
(only).
NOTE, a few paragraphs below, Tom Cutters
comments...and MINE...on how that boss was...or was
not...modified by BMW after
1974 or 1975 (We disagree on that point).
for other views, showing these parts lined up and how the neutral
switch works with them, see:
see:
http://www.largiader.com/tech/airtrans/
That article also has some photos in it that you may find
very useful in understanding the 4 and 5 speed transmissions in a
few areas.
**NOTE: use of the shift kit
REQUIRES use of the later LONGER neutral switch, or the neutral
switch
electrical functions will be in reverse of what they should be!
The later switch is 61-31-1-243-097, and a
spacer 61-31-1-355-262
is used... perhaps TWO.
The 1974-5 neutral switches have a shorter stem. If you
install the wrong switch, it does not work correctly!
NOTE! There is are TWO
sections in the ElectricalHints.htm
article on this website on the neutral switches,
neutral lamp,
starter circuit, and problems. It is complex!
Here is something from that
article, but please read the entire article! ::
ALL 5 speed neutral switches
are CLOSED in neutral, turning on the green neutral lamp
(enabling the
starter function if the starter button is pressed
on 5 speed transmissions). The reason for the shorter
and
longer neutral switches is that in the early shifting parts,
the switch rode on a section of the shifting cam that
was, in essence, a
projection, and the switch itself helped make the feel for the
'detent'. On the revised parts,
neutral is much more
positively felt, by the switch being in a 'valley' of the
shifting cam, hence the switch
needs to be longer.
There is a diode in the
neutral circuit. If that diode shorts, then the lamp is ON if the lever at the bars is
pulled.
There is also a peculiarity with the 1978-80
models, which have a master cylinder under the fuel tank.
These
incorporate a float switch, whose purpose is to illuminate
the brake failure light if the fluid runs low. The lamp
gets tested each time you start the bike, via a diode.
If
the diode shorts, and you are also low on fluid, the
starter
could theoretically energize.
Tom Cutter posted the following to the Airheads
E-mailing LIST in September 2003, and it clearly states what the
kit also does, and I quote
(typos corrected by me)
(comments
by me, snowbum, are clearly marked in BOLD RED):
"The kit includes a selector arm that has a second rail
which will then will allow shifting, albeit a little sloppy,
in the event that the spring fails.
(note
inserted here by snowbum: I do not believe that to be so,
the second arm being designed to prevent overshifts and false
neutrals). In my opinion, when the spring
is properly installed and the stress relieved, the failures
become non-existent. Nonetheless, the
new arm is a nice fail-safe
piece." (see above note by
snowbum, who believes the new arm is not a fail-safe piece as
such). Tom
later added the following:
"The repairs ...referred to are only necessary if one is
retaining the older shift pawl. If using the new shift kit, which
I highly recommend be fitted at the same time, the parts are
upgraded and don't need modification (Or they are supposed to, I
found one old
shift pawl in a shift kit recently). (Snowbum
says: Interesting, if true. The old pawls were
gone decades ago, no one else seems to
have found wrong parts in
the shift kits). I am trying to
describe this so it will make some sense, but basically, the
spring gets over-stressed
when it wraps around the boss on the
pawl. The boss can be ground to a smaller OD, and the spring
attachment point can be modified by
grooving the plate, to
prevent the spring coil-binding on the boss.
(Snowbum
says: The boss was a problem in the 1974, and maybe
some
1975 production, and the oversize boss was fixed no later than
sometime in 1975. I believe that, from then, the springs
break from improper heat treatment,
or fatigue, or too soft or too hard, maybe brittle....seems to be
a difficult part to
manufacture correctly?). Either
or both methods work fine. The important thing is to
assemble the shift plate mechanism, then pull
the shifter hook
arm back as far as it will go, while looking at the pawl spring.
If the spring is binding, it will be apparent. This must be
corrected." (snowbum says:
doesn't happen on 1976 and later).
NOTE:
An Airheads LIST inquiry on October 5th, 2011, resulted in Tom
Cutter's remarks about the23-31-1-231-619,
the original type of early shift pawl spring, the bend legged
type; replaced by 23-31-1-242-910, with straight legs. Tom
noted that you have to use the dog legged shift segment with it,
or the spring will bind.
10. The 4 speed transmission can be a devil to find
parts for, and to overhaul correctly. I strongly suggest
going to one of the experts
shown below, in particular Oak, Bob
Clement, Ted Porter, Tom Cutter and Matt Parkhouse. In
fact, those are my
recommendations for any BMW transmission. See
near the end of this long article a bit on those folks,
and how to contact them.
11. 5 speed transmission gear ratios:
| Gear | Stock | Competition/Race. The gear set is 23-21-1-233-427. I have never seen this gearset, and wonder if any were ever really made?? |
| 1st | 4.44 | 3.38 |
| 2nd | 2.86 | 2.43 |
| 3rd | 2.07 | 1.93 |
| 4th | 1.67 | 1.67 |
| 5th | 1.5 | 1.5 |
12. There is an additive that works
modestly well SOMETIMES to smooth the shifting,
particularly with transmissions with
the original older style
shifting parts. Do not use this
stuff with synthetic oil. It is Dow Corning M
Gear Oil Additive. Comes in quart
bottles. Shake well and use up
to 2% concentration max, DO NOT USE "UP TO" THE 10% Dow
suggests. The amount to use is about 18 cc for the
airhead
transmission. This stuff is VERY expensive. DO
NOT use with synthetic oil and do NOT add more than 20 cc!!!!
13. The 5 speed transmissions have, on the
input shaft, a cam and spring shock absorbing system, and one of
the gears, that has the cam
on one end, is 23-21-1-231-519.
This gear MUST be replaced if it appears to have worn such that
it looks even vaguely questionable;
the replacement gear from BMW
is hardened. READ the earlier
portions of this article on the complexities of changes to the
-519
gear....and the input shaft, etc.
14. There is a plastic roller on a shift lever in the
transmission, it is 23-31-1-231-572, and tends, over a long period
of time, to start
to fail; the steel one from the K is
23-31-1-451-087, and I have recommended it in the past. I
am not so sure about this, now, as I
have heard, ONCE, of the
steel K bike roller causing wear on its pin...and against the lever it
touches...and perhaps there is some
heat treatment variation on
that lever...or? NOTE: if the
roller fails, the transmission may well exhibit jumping out of
gear. This
can also happen if the associated spring
breaks. If a question comes up on this point, I defer to the
transmission experts mentioned.
At least one transmission guru, Ted Porter, is now using a
bearing, #688-RS, for that roller.
15. In 1977 BMW made changes to the
transmission. The slider gears shifting fork grooves
were made narrower, now 5.7 mm,
previously had been 6.5 mm.
The 3rd, 4th, and 5th gears now had square doglegs
(undercut). The detent spring was changed....and
it
has 5 turns. The cam-plate was changed. The casting
was changed for better selector fork shaft support for 3rd and
4th, and the shaft
which had been 100 mm is now 105 mm long.
16. Earlier transmission shift linkage had a foot shift
lever connection that had a rubber boot over it, and the linkage
is NOT
adjustable.....other than the foot peg, which is often found at
the lowest position, as the owner has big boots. Some will
install adjustable linkage,
or, horrors!, grind away the foot peg casting.
If you install the adjustable linkage from the ST and G/S models,
it bolts in place of the bent rod.
23-41-2-301-391. Drill the hole in the shift lever, as it
is just a bit too small in diameter. Use 1/4" drill.
Add the foam donuts 23-41-7-650-149 over each
of the ball joints, or replace your old bad ones. Keep it
all oiled.
Transmissions are best overhauled by an expert
with a lot of experience. For the person who definitely
wants to try doing a transmission, you
can do it under tutelage
or perhaps get Ed Korn's video, ETC.
Here are some old specifications....there are lots more specifications:
Axial float on all shafts: 0-0.1 mm (0-.004
inch).
Gear change lever shaft axial float on 4 speed: as above.
Fork bolts 17 footpounds.
Output flange nut 160 ftlbs (clean and dry on the
tapers!...absolutely NO residual oil!).
End cover nuts 6 ftlbs.
4-speed transmission, modification that I recommend:
The fix is to drill the center of that shaft at the back of the transmission, thread the hole, and add a large flat washer,
larger than the shaft diameter,
and use Loctite BLUE or RED on
the STEEL screw you will add to hold the washer to that
shaft. That prevents the shaft from moving
inwards.
Use some sort of goop sealant between the washer
and shaft/case, to stop any possible oil leakage.
IN DETAIL:
The FOUR speed transmission kickstarter idler gear shaft is
press-fitted into the rear transmission cover. There is a tendency,
particularly when
the gearbox is quite hot from a ride (which expands the
aluminum rear cover much more than the steel shaft!), for the shaft to move
inwards into
the transmission. Do NOT allow it to
move into the transmission! To do an easy fix is
often best, as the formal fix is removing
the rear output flange,
heating the rear cover, and ...with some experience
knowing what to do next, you remove that rear cover, and modify the shaft.
So, the easy
fix is to do the modification without gearbox rear cover removed; that is, it is
done BEFORE the shaft moves inwards...or worse, the parts inside
fall to the
bottom. The fix involves drilling and tapping the shaft, adding a
bolt or screw and large washer. In one instance I remember from
years ago,
the shaft had started to move, and the owner drilled the shaft, added a large
flat washer and bolt, and heated the rear cover, and
pulled the shaft back into
position. I don't recommend it, but it did work OK.
Removing the rear cover is better.
This mod has often been
done BEFORE there is any movement, withOUT removing the rear cover.
If you have the gearbox rear cover off when
doing this modification, then
re-assemble the rear cover by first cleaning the shaft and cover mating areas,
and then applying a drop or two of
Loctite to the shaft and cover as you
assemble the rear cover (heated, of course). Some other photos of
this job; and, a bit more information,
will be found in an article by Matt Parkhouse, in the August 2008 BMW Owners News, on page 38+.
BEARINGS:
4 speed transmission:
Output shaft, drive (rear) end, type 6204C3, 20 x 47
x 14 mm. This WAS part number 07-11-9-981-219, and that
changed to
07-10-1-468-880
Other (front) end, type 6403C3, 17 x 62 x 17
mm. This WAS part number 07-11-9-981-505, and that changed
to 23-12-1-338-795.
Used on both 4
and 5 speed gearboxes. SEE remarks below for 5 speed
transmissions!
Layshaft (also called the cluster shaft or
intermediate shaft), cover (rear) end, type 6203-C3, 17 x 40 x 12
mm, the part number is
07-11-9-981-214.
Clutch end double row type 3202 in some books, but
is 3203C3 (aka 5203), 17 x 14 x 17.5 mm. This WAS part
number
07-11-9-982-409, and that changed to 07-10-1-468-914.
Input shaft, both (front AND rear) are type 6304C3 20 x 52 x 15 mm. Part number 23-12-1-232-695. Used
on both 4 and
5 speed gearboxes.
5 speed transmission:
This is an EDITED repeat of a
NOTE, from considerably earlier on this page:
Regarding the 'special 6403-C3
bearing' for the front of the output shaft: It appears
similar to any other 6403-C3 bearing, but the front face
of the
inner race (forward edge of the inner race, the side of the
bearing which has writing on it) is cut with a 90° angle (much
smaller taper to
it than the rear face of the inner race) between
the face and the inner hole where the bearing slides over the
output shaft instead of the 6403-C3
bearing which has a tapered
angle. The forward taper is almost absent.
Perhaps this was done to minimize the possibility of bearing
creep
as the bearing is pushed against the retaining circlip by
5th gear. This modification may well have never been
needed. The regular bearing
worked fine, never a problem
with bearing creep leading to bearing axial overloading....UNTIL
BMW started leaving out the bearing retaining
clip. This
new bearing MAY be the accepted choice....but: The more
commonly accepted view is that the elimination of this cheap clip
and
associated groove caused the problems...AND...the last word I
had was that if one now orders the 'special bearing', you get a
STANDARD 6404-C3, withOUT the modified inner race face. The
'special bearing' was used only for awhile, and BMW went back to
the regular old bearing???
Continuing with the 5 speed transmission:
Output shaft, input (front) end, type 6403 (see 4
speed) (see above too!); and the output (rear) is 6304 (see 4
speed).
Layshaft (Cluster shaft or intermediate shaft), both
are 6304.
Input shaft: Uses special bearing #NU204E at
the front, and a 6304 at the rear
NOTE that the 6304THNC3 bearing is used, part number
23-12-1-233-807
ADDENDUM:
In 2005, Matt Parkhouse did a series of articles in
BMWMOA-ON, on overhauling the 5 speed transmission. GOOD stuff.
Anton's transmission article. Highly recommended
http://www.largiader.com/tech/airtrans/
It has a
listing of parts, some photos, including of the shift kit items, ETC.
This site will
further your education on the 4
and 5 speed transmissions. Anton also lists some of the
many changes BMW made
to these transmissions over the years, what
can and cannot substitute and what won't fit,
etc.
Here is a website page that tells you how to overhaul your 5 speed transmission
yourself. Whilst there are
plenty of tricks, etc., that are not in this
article, it SEEMS to be complete enough that YOU may be able
to do an overhaul.
This link was given to me, and I have NOT gone over the instructions step by
step.
I have also been informed that the nylon roller that someplace in
the article is mentioned as being
replaceable by a metal one (maybe he means the
K bike metal roller??)....has a wrong part, and the part
should be 688, not 628,
both being 8 x 18 x 5 mm.
http://jhau.maliwi.de/mot/gearbox.htm
However, see my much
earlier information on that....at item #14, above
Preloading the Shift Lever, what it does to make the transmission
shift smoothly!
I will try to simplify this....well, somewhat. Taking a bit of
license here too on the explanations.
Lightly preloading the shift lever can and does work on many
motorcycles, and it works on the Airheads and the Classic K
bikes. They are not the only vehicles where this works nicely.
PART of the good-effect is due to helping to slow the moving
parts just a tiny wee amount during the actual shifting attempt,
to help line-up the various parts.
For the Airheads, the transmissions, like most motorcycle
transmissions, use dogs on the end (sides, internal and/or
external) of some gears. When shifting, you are moving gears out
of mesh
or trying to put them into mesh at the gear's teeth, but you are
also sliding some gears along shafts (typically the gear is
sliding on a splined section) and the side of a gear is try to
mesh with the
side of another gear, by means of those side dogs; sometimes both
are male types, sometimes there are male and female dogs (that
is, the female ones are depressed inside the end of a gear).
Thus there are two types of meshing going on, one is the normal
gear teeth type of meshing, and the other is the sliding dogs.
End dogs are simply square sections on the sides of gears.
When two such dog sections mesh with each other, the gears are,
more or less, locked to each other.
A good cutaway of a transmission or a good sketch will show this
nicely.
Here is a really good website that shows how these types of
transmissions shift, animated, and also very good single photo of
a gear dog end, ETC.
Highly recommended:
http://www.gadgetjq.com/transmission.htm
As you try to shift your 4 or 5 speed Airhead transmission,
numerous things must happen at the same or approximately the same
time. Some parts must speed up, some parts must reduce speed, in
order to enable a meshing (of dogs and gear teeth). Gearbox
manufacturer's have engineers that get headaches from trying to
get gearboxes to shift smoothly, compounded by the fact that
motorcycle
transmissions do not have synchronizers. For motorcycles,
all sorts of friction effects from gears and shafts moving,
together with oil viscosity, etc., are involved. This is a DEEP
subject, and one
that BMW and its transmission designer-maker (Getrag) have faced,
with some strange results now and then ...like adding friction
producing O-rings on shafts. BMW transmissions, properly put
together, shift nicely, but other things can work against smooth
shifting....AT TIMES. One of those things is the heavy early
model flywheels, as the engine does not like to slow down as
quickly between
shifts, as does the later lighter clutch/flywheel models (1981+
with the new-style clutch carrier). Even the 1981+ lighter
clutch carrier assembly is heavy and has a lot of INTERTIA,
compared to most
multi-plate type clutches used on, for example, Japanese and
British (and American) motorcycles. Thus, slowing the
engine for shifting takes a small amount of extra time, but that
is very noticeable
to YOU, the rider. A lot of things must
happen in a tiny fraction of a second.
Aside note: in SOME types of racing, particularly drag racing,
decades ago, fast shifts were considered a must. Methods
included removing some of the dogs, increasing clearances where
the dogs
meshed.....and an "momentary ignition cutout switch" was
installed and was enough to allow the heavily loaded gears to
DEmesh and remesh (constant foot pressure on gearshift lever).
In fact, many a drag bike rider did not use a clutch!....the
shift lever was heavily preloaded, the switch literally "hit" and
the bike shifted.
You CAN shift your Airhead between gears by preloading the shift
lever and using the throttle....and no clutch.......but I
recommend NOT doing this.
If the gears/dogs do not line up rather closely at the exact
instant you want to shift, then it can take some additional rider
effort to get the parts to mesh quickly. Normally, coming to a
stop sign,
Airhead riders raise the rpm and shift downwards to first gear
BEFORE quite coming to a complete stop. Otherwise, you may
have to slightly engage the clutch or double clutch, play with
rpm,
etc. when you want to shift from Neutral to first gear when
starting off. In shifting downwards it is
normal to blip the throttle slightly. Experienced riders can
often shift downwards without the
loud clunk often heard from Airhead transmissions. Upward
shifting is usually easier, although the 1st-2nd transition is a
bit longer and longer-taking. BMW transmissions tend to take a
lot of
miles to fully break-in. The transmissions can also
shift differently, give a different 'feel' if the oil is changed
to a different viscosity grade, and, occasionally, just the
brand/model of oil has
made a difference. A Dow additive, in a weak amount, is
sometimes tried for balky shifting....sometimes it helps.
Note: it is entirely possible for two gears to try to mesh but
the teeth (or dogs) are directly opposite each other, that is, it
is square end of one tooth or dog against same on the other.
Unless you can get one of the two gears to move SLIGHTLY, you
will not get meshing. It is not unusual for this to happen; and
it can happen at the side dogs teeth, or the outer teeth of the
gears.
Side note: On kickstarter Airhead models, particularly early
ones, if you push the kickstarter down and it seems locked
(unless you use a LOT of foot pressure), I suggest you pull-in
the clutch
lever at the bars, and move the kickstarter lever downwards a bit
(easy) and then release the clutch. That allows proper meshing;
due to how the gear setup is. It also greatly reduces the
strain
on the parts from otherwise very excessive foot pressure on the
kickstarter lever........all of which is torque-multiplied by the
mechanical leverage, and applied to, perhaps, not overly strong
innards.
Bottom line: Pre-loading helps improve the friction, etc., to
allow closer rpm matching of the internal parts, and thereby
easier shifting.
DYI (Doing It Yourself)
****If you insist on overhauling your own 5 speed transmission, please understand that there are a lot of little things to know. However, many HAVE done an overhaul successfully; and whilst the overhaul might not be up to 'Guru' standards, it can be perfectly adequate. I have greatly resisted pressure to do step by step transmission overhaul articles, because of all the little details, which vary by year of transmission. On the other hand, I do wish to have something for you to look at. So, I offer the following URL: http://jhau.maliwi.de/mot/gearbox.htm
READ this entire article of mine all the way through, then go back and read that just-above URL.
After having read my long article you are presently reading, studied it, and are still thinking about doing it yourself, then, go back and read the just above linked-site; and this time click on all the various links, particularly at the bottom, then decide if you want to proceed. That article does not have all the finer details, many of which are in MY article, above.
Bottom line: If you are the methodical and careful type of person, YOU PROBABLY CAN overhaul your own gearbox (and, if you need some press or machining work, that is easily farmed-out).
Tools and video
for transmission work, and other work used to be available from
Ed Korn who previously did business as
Cycleworks, Inc. in town of Oregon, WI.
Ed did some
machine
work, had LOTS of tools
(and some parts) for everything from the Isetta cars,
through the /2 era, up until the Airheads stopped
production
in the late 90's. He had a rather extensive line of tools,
some VERY cleverly designed, and he had instructions, videos, all
sorts of stuff. Doing a run-through of his
website was informative to many folks. Ed sold the business
to Cycle Works LLC, located at
5805 Haskins Street, Shawnee, KS,
66216 (913) 871-6740. Contact the new owner
at: Dan@cycleworks.net
((NOT .com!!)).
The URL address
is still www.cycleworks.net
.............Dan will likely be very helpful.
The following are all known by me and recommended by me for ANY type of Airhead work:
"Oak" (Oak Okleshen). I can recommend OAK for ANY
type of airhead work.
Meticulous craftsmanship, and very knowledgeable.
Perhaps THE most
knowledgeable and METICULOUS craftsman on Airheads in the USA. Official
Friend of the Marque. MY mentor!
Be SURE to ask about how long your job may take.....he may be
backlogged.
22637 S. Ridgeway
Richton Park, IL 60471
askoak@aol.com
Anton Largiader in Charlottesville, Virginia
anton@largiader.com
Virginia Motorrad
www.largiader.com
Take a look at:
http://www.largiader.com/tech/airtrans/
That article has some photos in it that you may find very
useful in understanding the 4 and 5 speed transmissions in a few
areas.
Anton has two articles to look at, not overly clearly shown as
two different links, at least not in MY browser:
Look on the left side, and find 'transmission, clutch, final
drive'. Put your mouse pointer over "transmission" in
"Airhead transmissions and circlip problem". The word
'transmission' will be seen to be a link to his article. Click on
the word.
When finished looking at that article, go back to Anton's HomePage and this time put the mouse pointer over "circlip
problem" and click,
for the other article.
Ted Porter's Beemer Shop, on the West Coast. Ted
has a deservedly
solid reputation, and was with BMW for a long time.
Very knowledgeable. Quality work. His shop has a good reputation.
www.beemershop.com
34 Janis Way
Ste E
Scotts Valley, California
(831) 438-1100
Bob Clement.
Bob's Motorwerks
often just referred to as BMW-Montana
91 Blanchard Butte Rd.
Roberts, MT 59070
406-445-2044
bmwmontana@aol.com
Tom Cutter's Rubber Chicken Racing Garage.
1360 Colony Way
Yardley, PA 19067
shop: 215-321-7944
cell: 215-206-9787
Tpcutter@aol.com
Matt Parkhouse in Colorado Springs
hobomatt@aol.com or
bmwhobo@gmail.com
Matt Parkhouse may have some
excellent
used transmissions too.
The following are known to me
only by hearsay:
Charlie Johnson
BMW Motorcycle Service
(all models)
18145 Hummingbird Road
Wayzata, Minnesota
(952) 449-0357
Wuma, Inc (Guenther Wuest)
wuest@blueriver.net
6891 W. US Hy 150
Fredericksburg, IN 47120
812-472-3739
He ALSO does conversions to the 5 speed transmissions;
information on this conversion will be found in the SidecarURL.htm
page on this
website. Motorren Israel also does different
type of reverse gear conversions.
Motor Works, Inc.
1490 Island Ave.
San Diego, CA 92101
619-233-8875
motowrk@adnc.com
Brunos, in Canada
Revisions: (transmission ID and VIN updates are not shown below)
07/07/2008: all prior updates incorporated,
and, minor editing for clarity; and include groove depth; add
hyperlink to Anton's site
08/29/2008: Re-arrange the order of some items, change some emphasis,
explain a few things more clearly.
10/01/2008: Relatively major revisions. Whilst few if any specific
technical parts descriptions and details were changed, the
wording and emphasis was changed in numerous areas, and information on the more
accepted type of circlip caused
problems was expanded-upon, primarily as the result of someone contacting me who
gave input on things that were
not clear enough, or really required better explanations.
12/17/2008: Add photo and description of 4-speed kickstarter idler gear
shaft modification
01/17/2009: Add reference (2) in the addendum section
08/06/2009: Some modest updates for clarity, and some URL
references and recommendations....particularly for the 1974 year.
08/09/2009: Updated information in several places,
including item #14.
10/10/2009: Go through entire article, and try to clarify
as many details as I could
11/01/2009: update URL's and recommended repair specialist
list
12/27/2010: minor update for 1995 models.
01/28/2011: Clean up repetitive stuff...somewhat
02/03/2011: Add 16
06/13/2011: Add more links
08/01/2011: Add section on preloading and smooth shifting
and theory behind it; fix Cycleworks information
08/04/2011: Re-arrange article a bit, edit out some
superfluous repetition stuff
10/05/2011: a bit of additional commentary about the shift
pawl springs
12/24/2011: add two hyperlinks
04/28/2012: Begin revising article for clarity, particularly the pawl
spring and shift kit information, which had been scattered in the article.
© Copyright, 2012, R. Fleischer
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