Miscellaneous
section
miscl.htm
76
© copyright, 2011, R.
Fleischer
1. Hearsay has it that a better O-ring for the VM clock is the Harley Davidson oil pump cover O-ring #26434-76
2. Front
fork filling varies by model. Back in 1983, BMW had a
service bulletin about fork levels. Fork oil should be
replaced approximately every 10K or so. BE SURE to drain WELL,
moving the forks up and down a bit to be sure. Let them drain
overnight! There are TWO types of filling amounts sometimes
shown in the literature. A WET refill means the fork is
drained and refilled. A DRY refill means the fork was taken
apart for some reason, cleaned, and now to be filled.
Most of you will be draining and replacing the fluid, so the WET
refills are shown:
/5 and /6 and up to 1977 /7 265 cc per leg
Latest information is that performance will be better on those,
and up to 1980, with 221 cc per leg.
R65, R65LS 190 cc per leg (R65 and
R80 from 1986 use 300 cc per leg)
/7 from 1981; and all these to 1984: R80G/S, R80RT, R100,
R100CS, R100RT, R100RS 220 cc per leg.
R80ST 190 cc
R80GS, R100GS RIGHT leg, 440 cc, SAE 10;
LEFT leg, 410 cc, SAE 15
R80R, R100R 410 cc per leg
R80RT from 1985 300 cc per leg
R100RS and R100RT from 1987 320 cc per leg
You will probably find that a 4 or 5 weight or 7-1/2 wt oil is about correct, with a 10 wt usually too stiff. BMW's original red oil was really a MIL-spec oil, MIL5606, and was close to a SAE4, but BMW's literature here and there may indicate a 7-1/2 wt. oil. It is all in how it is measured, as there is NO official "standard" for fork oil. Oil viscosity from one manufacturer (non-MIL) is NOT the same as another. If playing with viscosities, I recommend staying with ONE manufacturer. CC means cubic centimeters, and is interchangeable with ML (milliliter). I highly recommend the use of a graduated flask...or...at least a known accurate container...when installing the correct amount of oil. Plastic graduated flasks are available cheaply. You can also use an old graduated BMW fork oil container. You can, on some models, such as my own 1983 and 1984 R100RT models, measure the oil level quite accurately with a piece of welding rod, about 1/8th inch diameter, inserted to the very bottom of the fork (you may have to jiggle the rod some to get it over the internal ridge and down to the bottom). For my models, the proper depth of oil is 11.8 inches.
Fork
gators: Some BMW's did not come with fork
gators. If you want to add some, see the Rancho brand of
shock absorber gators, in colors no less!.....but, FACTORY gators
are:
31-42-1-234-908; using clamps 07-12-9-952-121, and roll pins
07-11-9-941-470
3. From 1978, genuine BMW control cables are lined with a plastic material and should not be oiled or greased, as it collects dirt...yep, grabs it and sucks it in....and also some of the solvents in the lubricants are NOT compatible with the liner, and may cause the liner to swell. DO oil the end bits (barrels), as if you do NOT, you can cause fraying and eventual cable breakage at that point where the barrel attaches, due to the barrel now not rotating during use. That should be done after EVERY wash job. Some folks will grease those ends. It is important to lubricate the barrel ends not just at the throttle levers at the carburetors (if you have the Bing CV carbs), but also the clutch lever at the handlebars. The clutch cable at the rear of the transmission can have some grease packed around it...after cleaning.
4. Wobbles, Weaves, Tank
Slappers:
I would like to emphasize that a high speed wobble or weave is
NOT necessarily a 'tank slapper'. A TRUE TANK
SLAPPER is a wobble that keeps increasing in amplitude, to the
point that the front forks hit their stops, both left and
right. At LOW speeds, overly tight steering head bearings
will cause the bike to feel heavy handling, somewhat like
tracking rain grooves, or old style ribbed tire
feelings....and...require a lot more muscling around, and does
not steer so well by leaning. At high speeds an overly tight
steering head bearing adjustment results in about the same
feeling...leaning needs to be rather aggressive to work at all.
This type of problem is called WEAVING. The steering head is
USUALLY adjusted just about correct with the faintest
amount of weave at low speeds...perhaps around 30-40 mph it is
easily felt if present. This usually leaves the bearings in the
right adjustment area, to avoid the more dangerous high speed
problem of a too loose bearing. There
are TWO types of effects one might call wobble.
A relatively common one occurs at quite low speeds, you bump a
smallish rock or glance off the edge of a pothole, or some such,
and the front end does a quick jerk or wobble, often a goodly
fork movement. That one is generally NOT an indication of
anything being wrong. In slippery dirt and sand, if equipped, one
can turn on some steering damper (those are NOT for hard paved
street use...if you need it there, something is WRONG...although
I have nothing against you using it on severe rain grooves or
with very high winds).
At higher speeds and especially when pushing into corners, the
BMW airhead frame tends to flex, especially the junction of the
main frame and the rear subframe, but actually at a lot of places
including the front end. The old airheads were nicknamed Rubber
Cows for this effect. There are PARTIAL cures for this sort of
thing, and the later airhead models are stiffer. This
rubber cow could be positive or negative on a wobble trying to
start up. Problems with tires, bearing
adjustments, shock absorbers (rear AND front), etc....can make
situations turn bad.
A very good treatment of this subject, with a slightly different
slant, is in the February 2003 issue of AIRMAIL. ALSO, please
refer to articles on this website, for a considerable
amount of information.
Article 76-A on this website has
the REAL scoop on wobbles, weaves, and instabilities, if you have
an open mind, because it presents REAL tested information, and is
contrary to the old wives tales that abound: instability.htm
This is THE real information.
A terrific series of Airheads LIST
postings, with me participating to a goodly degree....and
covering weaves and wobbles in great depth, and highly
recommended is at:
http://www.airheads.org/index.php?Technical%20Tips+Discussion%20of%20%27Tank%20Slappers%27
In general, if everything is in good and properly adjusted
condition, instabilities are rather rare....except for tire wear
induced ones. The steering angle and trail on BMW's is set up for
stable touring and modest sporty riding, and tend to be very
stable...if everything is in good condition. Use of very hard
shocks, very stiff or wrong type springs, very heavy fork oils,
ETC, are to be approached carefully, as they may well have
unintended effects!! Especially in combination with
the rubber cow effect. When BMW designed our
airheads, they designed and tested the bike as a TOTAL PACKAGE;
...some instability or minor problem at one point, would be
negated by something else...all very complicated. Most
owners never run into this sort of thing, EXCEPT that some of the
literature will say ...for example....that BMW 'HAS TESTED....XXXX
TIRES...AND FOUND....XXXX'. Some tires are NOT appropriate. SAME
for some aftermarket modifications. ANY time one modifies one's
bike, YOU become the test rider.
AND, we all know there are FEW stock bikes as delivered. Be
cautious about tire pressures too.
An instability effect occurs on airheads, and this depends on
tires, bearings, model, and ESPECIALLY if equipped with fairing,
and MOST especially if a fork mounted fairing.....and... perhaps
with BAGS, and TRUNK/BACKREST. There will be some
instability felt as one approaches the critical speed where the
effect is pronounced. This is typically around 85
mph. A large part of this effect is due to air pressure at
various places on the bike. The entire bike will wobble, or
weave actually, often side to side, and someone following you
will definitely see this, yet you may well not feel it as badly
as the follower sees it. IF you knew how much you REALLY were
drifting around, you might freak out more! You WILL feel the
instability. It may well feel like a weaving, PLOWING effect,
hinged in the middle sort of thing....but not the heavy feeling
of weaving at low speeds. On the airheads, it tends to show up
first on downhill sweepers. It is almost always perfectly
controllable...one simply can ease off the throttle. I have NOT
seen one of these high speed weaves develop into a tank
slapper. That MIGHT be because the rider backs off
the throttle!
I was lucky in having two customer's bikes that did slappers, or
near slappers, consistently, and had a lot of fun analyzing and
fixing their problems.
Tank slappers, that much feared situation can, seriously, be
quite bad. It can result in an accident that is spectacular to
those following and witnessing it....like a high-sider can
be.
A tank slapper is an instability that presents itself as a small
back and forth oscillation of the bars/front end, that RAPIDLY
increases in size, not always at same frequency, and MAY result
in the fork going from its mechanical stop on one side to the
mechanical stop on the other side. MANY folks say they have had a
tank slapper when in actuality they have had a modest higher
frequency weaving, not hardly a true slapper. The problem with a
tank slapper is that we are generally not powerful enough....nor
fast enough....to compensate for the forces and speed of the
front end movement. Bikes that continuously want to
enter tank slappers should be repaired, NOW...but might be
gingerly driven, with damper engaged. Tank slappers were
never common, but the really old Brit bikes...and some
others....were known to have them now and then. Everything about
the bike can contribute, including bad shocks.
5. Drain plugs and their crush washers are available in oversizes. Example: The standard rear drive oversize plug is 11-13-0-007-163; oversize is 11-13-0-007-162; standard crush washer is 14 x 18 #07-11-9-963-213 and the oversize is 16 x 20 #07-11-9-963-259
6. I may, or may not, do a
fork overhaul article. But, some have asked about
modifications to the forks for more sporty...or
racing....performance. There are a lot of differences
between the forks over the years...MANY versions. I did
extensive rework of the /5 forks decades ago. TWO
modifications are going to make the dampening stiffer...in both
directions. You can braze up one or two of the rod
holes, and you can change the damper orifice to 15.5 mm, which is
31-42-234-506. A quite excellent ALIGNMENT article was done
on the forks by Randy Glass, complete with many illustrations,
etc.
this article is now on Duane's website:
http://w6rec.com/
7. Motor mounts:
There are 4 motor mount
spacers on airheads. The two plain
ones are identical and go on the rear mount bolt (the longer
bolt). There are two that have welded-on spring attachment
places....ONE has TWO such points, it goes on the left
front...and is where the sidestand and centerstand spring
attach. The curved part faces DOWN, curves towards
you. The other has only one attachment point, and
that is for the centerstand spring...it is fitted on the right
front...the hole facing rearward. There is a sidestand clip
that fits under the left rear nut, instead of the waverly
lockwasher that is on the other side. NOTE that all
spacers of any kind go between the engine and the frame.
torque nuts to 55 footpounds
8. Seats: There are
always plenty of questions on seats. What
interchanges fit, what does not, how the tank is affected, etc.
a. The /5 models and the /6 to 1976, had
the seat pins on the subframe facing each other. One had to
REMOVE one hinge to remove the seat. Be SURE to put
anti-seize on the threads!
b. The 1977 /7 "U.S." seat
pins faced in the SAME direction, and used CLIPS.
c. Subframes from the /7 will fit PRIOR
long wheelbase bikes.
9. For information on pressures, etc., for use in tire
changing...lots of information..see CATCH,
also see TIRES
(section 5)
10. There is an old
controversy over possible increases in combustion chamber
temperatures, ETC., when using premium gasoline's in lower
compression BMW airhead engines, where lower octane is supposedly
not needed. Gasoline burns at about the same rate under
normal, that is not detonating, etc., conditions. The output
(BTU) per gallon of premium gasoline is potentially....or even
likely...to be a tad LOWER than for regular. Therefore, I think
it is likely that SOME premium gasoline's WILL give LOWER gas
mileage than a regular gasoline will.....assuming here that the
engine will run properly on Regular grade gasoline in the first
place. Temper this with the fact that gasoline
formulas change, and also change summer and winter. Winter
gasoline tends to have rather volatile things like butane or
propane in them...etc. In the West, California in
particular, so-called oxygenates, such as MTBE and/or alcohol,
are added to most fuels in many areas. These
additions, GENERALLY cause 10% POORER gas mileage. They are
NOT good for your engine, carburetors, hoses, etc.
11. Later model rear drives have cast into them, near the REAR of the REAR DRIVE oil level plug, 'min..max' and lines radiating. Those are NOT oil fill lines, but lines for a pointer tab that fastened to the brake lever area to indicate lining wear. They are ignored on the disc brake rear drives.
12. Heated Clothing: I CAN NOT recommend Gerbings products, due to problems, reported from MANY, with personnel, workmanship, etc. I CAN recommend Widder products.
13. There are times when one has to remove one or two spark plugs and crank the engine. The spark plug caps internal metal must be securely grounded...such as to a cylinder fin, via the spark plug body metal. Just laying a spark plug with the cap attached, on the fin, is NOT adequate....if a bad connection...or the plug dropped off the fin, ETC.....this will allow very high voltages to be developed in the ignition coil(s), damaging them....and may damage other things, as on the 1981+ models with electronic ignition. The damage can show up MUCH later on. A very common use for ONE plug to be removed is the use of a air compressor of the type that fits a spark plug threaded hole. For dual plug ignition, you should ground the lower spark plug CAP by means of the same type of tool adapter as described in my synchcarbs.htm article. To ENSURE positively that the upper spark plug metal body is grounded to a fin, obtain a "Sash Rod Spring" from a hardware store, one with the package marked 24"-36" is about right, nothing critical. Reshape one end, and you have a nice addition to your on-bike tire repair kit.
14. Boyer versus Lucas Rita
Ignition: http://atlanticgreen.com/norton.htm
A couple of articles in the IGNITION section.
15. SEATS: moved to article #12; fuel,
miscl
16. How
to install the pesky speedometer cable rubber boot at the
transmission output area:
Push the rubber back on itself and push up onto the cable
with the large end upwards (pushed back on itself). You
will then be pulling the large end downward, so the small end
stays upwards. I lubricate the cable and the top of the
rubber (inside and outside) with copious amounts of silicone
grease, and after it is installed and the large end pulled back
downward, I push the top portion down a wee bit, clean very
thoroughly the cable and the rubber boot top with acetone.
Then pull it slightly up to normal position, wipe with acetone
again, and I put a bit of black RTV around the top to make a 100%
positive sealing against water going down the cable and inside
the boot. After the RTV cures overnight, I use Armor-All or 303,
or whatever I have here, on the entire boot...which prolongs the
life to many years. The rubber compound is adversely
affected by smog, sunlight...
revisions:
All updates to 05/30/2006
04/14/2007: Seats information now in article #12
04/22/2007: add #16 to this page
01/07/2008: fix hyperlink in #14
01/08/2008: remove Randy Glass' website url, it is dead
05/22/2010: change article number
03/29/1011: Remove all information in item 7 but the motor
mounts. The information on stands has been moved
to another article.
© Copyright, 2011, R. Fleischer