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5 speed transmission,
neutral switch replacement.

Copyright 2014, R. Fleischer

4 speed transmissions have an internal neutral position contact, and a single wire fastens to it... on the rear of the transmission.  This article is not applicable to the 4 speed transmission, which does NOT have the various complications of the 5 speed neutral switch circuitry.  The 4 speed transmission neutral switch is used ONLY to indicate neutral by illuminating the neutral lamp.

The switch at the clutch lever on the left handlebar on 5 speed transmissions is not the true neutral switch to illuminate the neutral lamp, although it functions with the real one, but not in the same way.  The switch under discussion in this article is the switch on the bottom of the 5 speed transmissions. 

Don't do a neutral switch replacement unless you are SURE it is transmission oil that is leaking from the area, or you are sure that the switch has electrically failed.  You may be able to repair a mild weeping or small leak from the switch itself, using the procedure shown later in this article. 

There are TWO versions of these switches, so be sure you get the right one for your bike.  The switch function was reversed in the 1976 model year, and they look sort-of similar.

The stock 1974-1975 5 speed transmissions used a 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 were OK numbers.  A thin washer is used, about 0.5 mm or so on this early switch.   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.  Some 1976 transmissions were earlier 1975 models but may have the earlier "1974" switch.   The change from one switch to the other did not occur exactly with the change of model year, so be careful.

For the 61-31-1-243-097 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, but this is not important. 
If you forget to install this ~2mm washer the neutral lamp will NOT work correctly, no matter which switch you have installed ...and you may have shifting problems.  The reason the switch was changed is that the updated transmission shifting cam uses valleys to positively locate the switch plunger; while in the prior version the switch plunger rested on the 'mountain-tops' on the shifter cam.

If you have pulled the transmission rearwards to, perhaps, grease the input splines, it is then easier to remove and replace the neutral switch.  If the swing arm is pulled to the rear somewhat, you have more room.  The effort varies with the models over the years.  If the transmission is out and on the workbench, the job is very easy. do NOT have to pull the transmission backwards NOR do you have to remove it, to replace the switch (or, try to seal a leak from it).  With the transmission in place on the engine, you MUST remove the long aluminum spacer in order to get to the switch.   More on that, below.

Switch leaks & preparation for installation:

The switches were made with electrical spades pointing sideways (later types), and also made with them pointing downwards (early types).  With the downwards type, it is easy to use a deep socket or wrench.   With the sideways type, you will have to use an open-end wrench unless you have made a special socket tool.   DO NOT bend nor pressure the spades!  Do not warp the body!

Even brand-new switches can leak right after installation or after awhile. There is something wrong with the construction. BMW has been informed.  So far, no BMW fix.  The type of leak usually seen is a very slow weeping at the junction of the insulation and the metal body ...or ...leaking from the spades where they go into the body.   I have heard from several sources that Motobins sells copper (brass?) bodied types that do not seem to leak.   HOWEVER, a noted Airhead Guru, Tom Cutter, reported on 05/04/2015, on the Airlist, that he bought twelve of part 76700A.  Seven were dimensioned incorrectly so that they did not switch reliably. Two leaked immediately on installation. The last time he ordered, they filled the order with OEM switches.  Tom reported on 07/01/2015, that he had purchased SIX from Siebenrock; and of that SIX, 2 did not work, 2 had threads too long, and 1 leaked.

HOWEVER, I have had reports of excellent results with THESE:

I recommend that EVERY switch, new or used, have the following done to it BEFORE installation or re-installation:

I will NO LONGER install ANY of these switches, new or used, from any source, without doing the following; and, remember, do not over-tighten NOR bend the male spades.

Using a dental tool or other sharp small thin 'tool', get right into and lightly scratch a fair amount at the junction of the metal body and bakelite insulation ...where body joins the bakelite insulation. If you want to seal the spades, do it around them too. THEN, use a tiny piece of fine sandpaper, and rough-up the metal and especially the bakelite insulation, of that junction of the metal body (and spades, if so doing) to the hard plastic insulation section.  The idea is to sand the junction, including the metal and the plastic, for maybe 1/8" width minimum, right into the junction ...and then clean that area with a strong evaporating solvent.  NON-oily acetone is what I use, NON-oily means NOT using your wife's fingernail polish remover. You can use MEK, etc.  Then apply a fine to moderate line, all-around, it need not be all that wide, of a thin viscosity 'wicking' Loctite.   I like to have the switch warm to medium hot.   Do this with the switch standing with the terminals upwards, threaded end downwards.  Let sit, a full day, preferably in your warm house.  THEN clean the junction with a thin rag with acetone or MEK, etc. 

I THEN apply epoxy to the junction, completely around. You do not need large amounts.   Either 5 minute or 24 hour epoxy. I prefer a slower-curing epoxy.   Let it cure one full day, even if the 5 minute type.  THEN install the switch ...being careful to install the proper washer, and  do NOT over-tighten.  If you over-tighten, you can distort the bond and it may leak. The tool you select may depend on the particular switch and terminals orientation. BE SURE THE SWITCH WORKS PROPERLY.  AS YOU SHIFT GEARS THE NEUTRAL LIGHT SHOULD COME ON ONLY IN NEUTRAL.

Most folks with an electrically bad, or oil-leaking neutral switch, should do as follows:

FIRST, determine that the switch really is leaking oil; or, that the switch is actually bad.  Testing is relatively easy.   The rest of this section assumes the switch is going to be removed and repaired for leaking ...or possibly replaced due to switch failure.

Place a support under the engine oil pan, perhaps sturdy large blocks of wood. Be sure to support the oil pan on something like wood blocks.  Loosen the front engine mounting stud don't have to loosen it more than a full turn.  These steps will usually make the follow items easier to do.

The long round aluminum spacer underneath, that the rear motor mount stud goes through, is in the way for access to the neutral switch. The rear long steel engine mount stud passes through the frame, the spacer, and the frame again. There is a washer and nut at both ends of this long threaded stud.  You need to remove that stud and then remove the long aluminum spacer.  Replacing the switch is then relatively easy.   The question often is how to remove that long stud, sometimes it is quite tight.  I sometimes just use a soft brass or aluminum rod I have, with a dead-blow hammer.  You probably don't have such rods, so, here is a nice method, one that you may want to put into your personal memory bank:

The following is called the "draw-bar method".  This method is sometime used to draw out piston pins, etc ...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.

Drawbar method:
1. Remove the nut & washer from one end of the rear engine stud ....let us say the right side.  WHICH SIDE IS UNIMPORTANT,  JUST PICK THE ONE YOU LIKE. You can use oil if you wish on the stud you removed the nut and washer from, in this example, the RIGHT-HAND side.   Sometimes oiling helps when pulling/drawing out the stud.   Use additional oil as you proceed.

2. Tighten up the remaining nut this case the left side nut ...until you just about, but have not, reached the end of the threads.  Almost always the stud will not rotate as you tighten towards, but not TO, the ends of the threads, after all, the stud usually has a lot of friction, WHICH IS WHY YOU ARE USING THIS METHOD.  If the stud rotates easily before the nut reaches the ends of the threads, it likely will come out easy, or at least in part easily use of a rod and dead-blow hammer on the right side. 

3. Remove the left side nut & put any convenient metal spacer you have lying around over the stud, leaving enough room to enable 3 or 4 threads, A SAFE NUMBER of 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 ...pieces of pipe ...whatever.

4. Again tighten the nut to near the end of the threads. Repeat by adding spacers, washers, sockets, whatever. Oil the right side if you want to try that to enable the stud removal.  I use a spray can of light oil. Notice that each time you do this 'drawing-out', the stud will be DRAWN OUT more to the left.  Continue and 'draw out' that stud until you can pull it out.  Clean the stud carefully want it SMOOTH when you reinstall it later on. I usually do a sort-of coarse polish job on the stud with a rotary wire brush.  If you have not loosened the front stud a bit, and blocked up the pan, this drawing-out can be more difficult.

5. Clean the bore with a solvent and then use a rat-tail brush or shotgun cleaning brushes to clean the area the stud fits through and clean the bore again. You don't have to do this step now though.

6. The next thing is to remove the long aluminum spacer. It is almost always wedged in TIGHT!  It needs to be reasonably tight when replaced.   You will have to do some prying, so be careful, do NOT bang or pry on anything you shouldn't!  Usually one simply pries a TINY bit at one end, then the same at the other end, back and forth, working the spacer out slowly.  I like to leave no marks, and certainly not break or crack anything, especially the transmission fins/etc!  I may use a small piece of wood, or whatever is handy, to avoid pressing on the wrong areas.   A proper shaped pry bar will also work nicely, consider padding it or using a piece of wood, etc.  Don't injure fins, etc.

During this process of removal of the long spacer Do NOT push the spacer forward ...the whole idea is to remove it towards the rear for removal.

SOMEtimes just loosening the front motor mount will enable the spacer to loosen up some!!....due to various side forces and fitment of the already did that, and supported the pan,  ...YES?

7.  You need to drain the transmission oil!  If the oil has 10K on it or more, don't save it, plan on installing fresh 80W90 GL5 oil.

8.  With the spacer removed you now have access to remove & install the new & PROPER part number switch (suitably SEALED FIRST, as recommended).

9.  Don't forget to install the PROPER WASHER,  using the special washer with the later style switch. 

DO NOT over-tighten
the neutral switch!   BE CAREFUL not to distort the switch body nor the spade connectors.  With the switches that have prongs downwards, that is easy, use a proper depth of socket.  DO NOT OVERTORQUE.
***If the switch is OK, but just weeping or leaking a bit, you can try to fix the leak. 

10.  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 switch male spades, squeeze, SLIGHTLY, the females.   It is a VERY good idea to test things 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 likely installed the WRONG switch.  BUT...check to be sure you did not pinch wires.   Both styles of neutral switch closes their 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 styles of switches has its plunger OUT for turning the switch ON, the other has the plunger inwards to turn the switch ON.

The two push-on wires to the switch can be interchanged at the switch; either can fit to either terminal.

Some switches seem poorly made internally, and do not work properly ...yes, brand-new ones.  Others have seen this too, with the brass switches from aftermarket suppliers.

RE-installing the long aluminum spacer:
Read this through ahead of time, and then you will be ready when the time comes.

1.  CLEAN the long aluminum spacer if not done already, 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 the contacting face.  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.  I have a lathe, and do it with a fine mill file in the lathe, but have done it in drill presses, and in my hand too. Remember: NO sharp edges.

2.  FREEZE the spacer AFTER spraying or otherwise coating the INside of it with any handy thin oil.  The freezing causes it to SHRINK in length.  In shops, we might quick freeze it to very cold, 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.

4.  Grease or oil the CLEANED stud (I first use a wire wheel or wire brush on the studs if cruddy) very lightly over its full length; then install one washer and one nut on one end, such that NO threads are exposed outboard of the nut, but as many threads engaged as nut allows. I freeze that stud first before installing; but you probably don't really have-to.

5.  Install the well-frozen aluminum spacer FAIRLY QUICKLY and EVENLY, I use thin leather gloves.  Don't tilt the spacer, install it as squarely and quickly as you can,  ...using a plastic mallet or brass hammer, etc. Try to line up the frame and spacer holes as closely as you can, using #1 eyeball.  Use a round tool of some sort (axle tommy bar?) if you need to, to align the holes of the frame and spacer.  DO NOT injure the transmission case fins, etc.

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.  You may have to move the rear of the engine up and down a small amount; usually I do not have to.

6. Even up the stud, side to side, install nuts & washers, torque the nuts, keeping the amount of threads proud of the nuts approximately the same on both sides.  55 foot-pounds.

7.  Don't forget to re-torque the front engine stud nuts that you previously loosened some!!

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, add part numbers from prior article on same subject, inadvertently left out.
12-05-2011:  add information on sanding and epoxying even brand new switches.
02/04/2012:   clarify neutral switches and their washers.
10/11/2012:   add QR code; add language button; update Google Ad-Sense code
11/25/2012:   Clean up and revise slightly for clarity, order of events.
04/02/2013:   Minor improvements in clarity; also removed language button sometime in 2013
05/04/2015:   Add Tom Cutter's remarks about the Motobins switches; and, from Alan, bmw2valve info. 
07/01/2015:   Additional updating for clarity.
03/08/2016:   Update meta-codes, fonts, colors, layout, small changes for clarity.

Copyright 2014, R. Fleischer

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Last check/edit: Sunday, March 12, 2017