Replacing a 5 speed neutral Switch
(and, selecting the correct switch)
neutralswitch.htm-25
© Copyright 2012, R. Fleischer
There are actually TWO neutral switches used on later models. One is the switch at the clutch lever on the left handlebar. That is NOT the neutral switch under discussion in this article. The switch under discussion in what follows is the switch on the bottom of the 5 speed transmissions. (( 4 speed transmissions have an internal neutral position contact, and a single wire fastens to it on the rear of the transmissions. This article is not applicable to the 4 speed transmission, which does NOT have the various complications of the neutral switch circuitry))
Don't do a neutral switch replacement unless you are SURE
it is transmission oil that is leaking from it, or that the switch has electrically
failed. Some folks deal with minor leaks at that switch by
cleaning and then using an epoxy at the switch.
You can short across the switch wires on the 5 speed transmission
switch to determine if the switch
has failed or not. This is a bit difficult to do without long forceps or
similar to remove the wires on the 5 speed....but the 5 speed models have a two-conductor cable
along the subframe, and you can short the cable connections to ground, one
such connection lights the oil lamp,
the other one the neutral lamp.
As noted, the neutral switch is on the bottom of
the transmission on the 5-speed transmissions. There are
TWO versions of these switches, so be sure you get the
right one for your year bike. The switch function was reversed in the 1976
model year, and they look almost the same (unless you had them side by side).
If you have the shift kit installed, you use the late type switch.
The STOCK 1974-1975 5 speed transmissions used neutral switch
with a somewhat shorter stem than the 1976 and later, the older switch was
61-31-1-352-153; which became 23-14-1-352-153. Along the way was
61-31-1-358-142; all are OK. A thin washer is used, about 0.5 mm or so.
The 'books' will show that washer as size 12 x 15.5, and the number as
07-11-9-963-130. That washer was used at two other places on Airheads:
(1) 4 were used, two on each side of each of the banjo bolts for the oil cooler;
(2) the same -130 washer was used on some fork lowers, the center bolts at the
bottom.
The 1976 and later transmissions use switch 61-31-1-243-097.
For that -097 switch you must use ONE special 2 mm thick washer (do NOT use a
common drain plug gasket washer!), which is 61-31-1-355-262.
Reports of BMW having shipped the wrong part have been seen.
Tom Cutter measured a new one and it was
19.8 mm x 12.35 mm x 1.89 mm.
Original new ones, which might fit better (?) are probably 2.0 mm
thick.
NOTE: The change from one switch to the other did not occur exactly with
the change of model year, so be careful, and note the commend above on using the
later switch with any shift kit installation.
The reason the switch was changed is that the updated transmission shifting came uses valleys to positively located the switch plunger; while in the prior version the switch plunger rested on the 'mountain', so-to-speak.
If you have pulled the transmission rearwards to, perhaps, grease the input splines, it is a bit easier to remove and replace the neutral switch on the 5 speed transmission. If the swing arm is pulled to the rear somewhat, you have more room. This varies with the models over the years. If the transmission is out an on the workbench, the job is very easy.
HOWEVER...most folks with an electrically bad, or oil leaking
neutral switch, will do, or should do, as follows:
FIRST, place a support under the engine oil pan,
THEN loosen the front motor mount a bit.
With the transmission installed in place on the motor, the long aluminum spacer
underneath, that the rear motor mount stud goes through, is in the way. That
long steel engine mount stud that passes through it and the frame. There is a washer and nut at both ends.
FIRST remove that stud and remove the long aluminum spacer.
Then replacing the switch is
relatively easy. The first question that comes up is how to remove that long stud,
sometimes it is quite tight. NOTE that
sometimes it relieves a bit of various pressures to LOOSEN the
FRONT motor mount a small amount.
The following is called a draw-bar method, for removing the rear
engine mounting stud
if quite stiff in the frame and spacer.
This method is sometime used to draw
out the piston pins...and a modified method is used at other places, such as pulling
off the head and cylinder, when they rarely don't come off easily. ANOTHER method
is to use a rod and a dead-blow hammer (for the stud!).
I approve of any of these methods. Be sure to support the oil pan and then
loosen the front engine mounting stud, that really helps.
Drawbar method:
1. Remove the nut and washer from one end of the engine stud.....let us say the right side.
2. Tighten up the other nut....in this case the left side nut... until you just
about reach the ends of the threads. Almost always the stud will not
rotate as you tighten towards (but not TO) the ends of the threads,
after all, it is stuck! If the stud rotates, it likely will
come out easy, or at least in part easily...by use of a rod and
dead-blow hammer.
3. Remove the left side nut and put just about any metal spacer you have lying around over the stud, leaving enough room to enable at
least 4 threads to be engaged by the nut. You can start with some large washers, then graduate to any old socket that
fits, with a washer if needed; or...piece of pipe ...whatever.
4. Again tighten the nut to near the end of the threads. Repeat
by adding spacers, washers, sockets, whatever. Notice that each
time you do this, the stud will be DRAWN OUT more to the left.
Continue and 'draw' out that stud! Clean the stud
carefully....you want it SMOOTH when you reinstall it later on.
I have used shotgun cleaning brushes to clean the area the stud
fits through.
Now that you have that stud out, the next thing is to remove that long aluminum spacer. It is almost always wedged in
TIGHT! You will have to do some prying....be careful,
do NOT bang or pry on anything you shouldn't! Usually one simply pries a TINY bit at one end, then the other end,
back and forth, working
the spacer out slowly. I like to leave no marks, and certainly not break or crack
anything. I may use a piece of wood, or whatever is handy, to avoid
pressing on the wrong areas. A proper shaped pry bar will also work nicely.
Don't injure fins, etc.
HINT!!:
Some have asked if it is possible to spread
the FRAME a very tiny amount, using some sort of home-made tool. YES! I
have done this with one of those types of tools used to tighten a car engine
drive belt....it fit between two pulleys...improvising a modification to that
tool. I loosen the front engine mount a couple of turns
first, so a support under the oil pan is a must. It may be possible to wedge a piece of wood between the frame
members a bit. Just do NOT do more than
a FEW thousandths on an inch, so the frame will spring back. SOMEtimes just
loosening the front motor mount will enable the spacer to loosen up some!....due
to various side forces and fitment of the studs.
With the spacer removed you now have access to remove and install the new and
PROPER part number switch and
don't forget to install the special washer used with the later style switch. DO NOT overtighten that neutral
switch! After you replace the
switch/washer, and before you install the aluminum spacer, DO NOT FORGET TO INSTALL THE WIRES!
If they do
not fit tightly onto the male spades, squeeze, SLIGHTLY, the females.
It is a VERY good idea to test things electrically...be sure the switch is
working, and DO check that you have the neutral lamp ON in neutral....and not OFF in neutral!
(If you have the lamp ON in all 5 gear positions....you installed the WRONG
switch!); or you pinched or crossed the wires. The neutral switch in all cases closes its circuit
to turn the light on. The difference has to do with the
shift kit cam changes. That is, whether or not the
switch plunger sits on a hill, or a valley of the cam, in
neutral. Thus, the switch operation is reversed between the
two switches...one has its plunger OUT for turning the switch on,
the other has the plunger pushed inwards to turn the switch on.
NOTE that the two push-on wires to the switch can be interchanged
at the switch; either can fit to either terminal.
Special note: Brand new neutral switches have been seen to leak soon after installation. This type of leak is a very slow weeping at the junction of the insulation and the metal body. I am now recommending that EVERY switch have the following done to it BEFORE installation. Use a tiny piece of fine sandpaper, and rough-up the junction of the metal body to the hard plastic insulation section. ALSO, use a dental tool or other sharp object, to get right into that crack/junction. The idea is to sand the junction, including the metal and the plastic, for maybe 1/8" (or more), and then clean that area with a strong evaporating solvent (NON-oily acetone), and apply epoxy to the junction. Either 5 minute or 24 hour epoxy is OK; JB weld is also OK. Let it cure overnight, even if the 5 minute type. THEN install switch.
WARNING: Do NOT push the spacer forward...the whole idea is to remove it to the rear.
Now it is time to
RE-install that
long aluminum spacer. Here are tricks to ensure success:
Read this through ahead of time, and
then you will be ready when the time comes.
1. CLEAN the spacer, inside and outside. I use a gun cleaning
kit and bore patch with solvent. Good use for Hoppe's! Put a SLIGHT smooth radius
(16th or 32nd.) on the sharp end edges. This does NOT mean a 1/4" radius! What you
want to do is smoooooth the edges at
both ends, so it installs easier, yet not much end surface area
will be removed from contact. A piece of sandpaper or a mill
file works nicely, or even a drill press with sandpaper or mill
file.... if you don't have a lathe. Remember: NO sharp edges.
2. FREEZE that spacer AFTER spraying or otherwise coating the INside of it with any handy oil. The freezing causes it to SHRINK in length. In
shops, we might quick freeze it with an old CO2 fire extinguisher.
YOU can use your household freezer....or CO2.
3. Check the transmission area, and if any sharp edges, also remove those,
carefully. You want that spacer to install
fairly easily, but certainly not loosely!
4. Grease or oil the CLEANED stud
(I use a wire wheel on the studs if cruddy) very lightly over its full length; then install one
washer and one nut on one end, so that NO threads are exposed
outboard of the nut.
5. Install the well-frozen aluminum
spacer FAIRLY QUICKLY and
EVENLY, I use thin leather gloves.....don't cant it (install it as squarely as you can)
...using a plastic mallet or brass hammer, etc.
Try to line up the holes as closely as
you can, using the #1 eyeball.
Without waiting more than a minute or so, fully install the
stud using a brass or plastic hammer, on the nut end. If you had the
internally lubricated aluminum spacer
well-eyeball-centered, still frozen, and the stud greased or
oiled, this will go relatively smoothly.
In some cases I have loosened the front engine mount slightly...but only if the
engine was supported at the pan; you may already have that front
stud loosened anyway....it sometimes makes it easier.
6. Even up the stud, side to side, and install nuts and washers and
torque the nuts tightly, keeping the amount of
threads proud of the nuts roughly the same on both sides.
55 footpounds is about correct.
Revisions:
04-17-2003: add .htm title; clarify details
07-07-2003: expand and clarify procedure
08-24-2004: add techindex I.D. number; clarify some details
02-24-2005: clarifications, and again in April 2007
11-20-2010: Clean up article, and add part numbers from a
prior article on the same subject, inadvertently left out of this
article.
12-05-2011: add information on sanding and epoxying even brand new
switches.
02/04/2012: clarify neutral switches and their washers.
© Copyright 2012, R. Fleischer