5 speed Neutral Switch prep work

I learned this lesson the hard way.
Apparently many of the neutral switches, when purchased new, are faulty and are prone to leaking. Not knowing this, I went ahead and installed a brand new switch into the transmission, then installed the tranny onto the bike, added transmission fluid I and started to break the engine in.
After the first ride, I realized that there was a small drip of transmission fluid coming from the neutral switch.
It would not be such a big deal on a late 70’s airhead but the engine case of a /5 is different then other airheads and requires that the transmission gets pulled back about 2 inches so the switch can be removed and replaced.

Keep in mind a few things…
•/5 BMW’s had 4 speed transmissions so this may not apply to most people. I upgraded this bike to a 5 speed.
•There are two types of switches for the two different 5 speed transmissions. They work differently. I think you can tell them apart because one has the electrical prongs facing sideways, the other has the prongs straight.

On a late 70’s airhead, there is a large spacer on the engine case under the transmission. You can wedge blocks under the oil pan to keep the engine from sagging, then drive out the rear engine mounting stud until the large spacer can be removed, then you have access to the neutral switch for an easy replacement.
(Click photo for a larger version).
R100sNeutralSwitch

On a /5 BMW, the engine block doesn’t have the spacer. You will have to take the airbox cover off, remove the swingarm, rear wheel, disconnect the transmission from the engine, etc…
While you are in there, it is a good time to lube your transmission splines and re-lube your swingarm bearings!
slash5W5speed

Here is a new neutral switch and I am going to seal it with some JB weld. You can also use epoxy or bubble gum (just kidding about the bubble gum).
NeutralSwitchimage_1c

I took some sandpaper and exacto blades and scuffed up the plastic surface and part of the switch near the plastic. After I scored everything pretty good, I cleaned it up with some acetone. NeutralSwitchimage_2C

I mixed up a batch of JB weld and coated all the plastic and part of the metal. I may have went overboard but better safe then sorry. I don’t want to have to replace the switch again.
Allow for at least 24hours to dry.
NeutralSwitchphotoCoated

Now it is time to drain the transmission oil, pull the rear of the bike apart, slide the transmission back and replace the switch.
This could be a 15-30 minute job on a R100S. Unfortunately it will take much longer on the /5.
Don’t forget to buy new crush washers for the transmission plug, neutral switch and transmission fill plug. They are only a few extra bucks.

Transmission Install

A Transmission install is actually not difficult.

Step #1 is making sure the swingarm is unmounted from the frame. It can remain connected to the shocks.

I then took caution to protect the frame:

Protection. Notice the rags too:

Time to prep the transmission. It helps if the shifter and the clutch arm are removed. In my case, i removed the shifter but left the clutch arm mounted:

Time to lube the splines. Make sure the splines are clean of dirt and grime. I use a BMW moly grease. It is sticky stuff. :

Keeping the swingarm and rear wheel pulled back, gently lift the transmission into place. It may take a small wiggle here and there to get the splines to mate with the engine.

Make sure the top right bolt of the engine housing aligns properly with the transmission housing as you mate the splines into the clutch:

Time to tighten everything down.
You need a M8 nut and washer for the top right engine stud bolt.
a M8 x 40mm bolt and washer for the top left mount. (Note, i am not installing the BMW airbox. If i was, there is a retaining clip that mounts to the top left bolt along with a washer intended for the airbox).
a M8 X 85mm bolt, washer and nut for the bottom right mount
and a M8 x 40mm bolt and washer for the bottom left mount.
A 6mm hex socket and wrench does the trick along with a 13mm wrench/socket.

Lastly before you mount the swingarm, Make sure you attach the driveshaft boot. Notice the different ends of the boot. The round end is for the transmission, the oval/rectangular end is for the drive shaft.

Next step… aligning and mounting the swing-arm… stay tuned!

Reassembly of transmission and final drive

I’m definitely not going to take on these daunting tasks myself.  Just look at all those parts!

Someday when i have lots of extra time and extra transmissions to experiment on, i’ll try to figure this stuff out myself.

But for now, they are going to the hands of  an expert.  Luckily everything fit in the saddlebags of my R100s.

Somehow, those parts are going to fit into that shiny housing.

Final drive guts

Trany guts. Looks like a clock exploded.

BMW parts inside of BMW bags.