Vintage BMW Motorcycle Owners

The guilt and the curiosity were eating me alive.
I couldn’t wait any longer to receive the address and deliver the gearbox (sorry Mr. S), so I decided to use the museum shop to open the gearbox myself and try to find out what is wrong.



Following the Barrington, if you don’t have one you should get one immediately, with the help of Dave and Peter I open the gearbox.

The Barrington shows a very simple tool to separate the cover and Dave used the vertical mill to fabricate one.








Since the kick starter lever was stuck in place, we couldn’t move it out of the way as instructed by the Barrington, but with a lot of patience we manage to separate the cover.







It took a lot of heat, a little violence and the pulling of the outmost bearings to remove all the shafts.



It looks like cage of the input shaft bearing failed. It broke apart tangling itself in the drive gear preventing the shaft from rolling freely, seizing the gearbox. All the balls are shift together to one side.











That is what I can see, I don’t know is this is the cause or the consequence of something else.

What do you think?

That looks like it is the problem. It also looks like you got off very easily and did not destroy anything too badly.

Almost all bearing cage failures are due to poor installation. In that case that would mean not heating the case as much as it should have been heated and forcing the bearing in. It is fairly common and I have done it myself in the past. Some cages are more prone than others to breaking.

jwonder wrote: ↑

Sat Oct 09, 2021 5:44 pm

That looks like it is the problem. It also looks like you got off very easily and did not destroy anything too badly.

Almost all bearing cage failures are due to poor installation. In that case that would mean not heating the case as much as it should have been heated and forcing the bearing in. It is fairly common and I have done it myself in the past. Some cages are more prone than others to breaking.

Since I have some extra time in hand, I continue with the investigation.
The shifting mechanism is a mess, cam plate bend, detent lever spring crunched, there was some serious pressure put in the shift lever.
Already straightened the cam plate out in relation to its gear. Will need springs and bearing, the shifting assembly is reinstalled in the housing. The front input bearing is what failed and locked up. Lucky it did not crack the case.

Gear Box ready.

The front input bearing is what failed and locked up, but the main damage was the shift cam, it put too much force on the shifter.


The shifting mechanism was a mess, cam plate bent, detent lever spring crunched.
There was some serious pressure put on the shift lever.

Cam had to be straightened and re-staked in position.
Also input shaft rear shock coupling had lost some of its hard facing. Replaced it with good used one.
I straightened the cam plate out in relation to its gear and installed new springs.
Lucky the force didn’t crack the transmission case.

I ordered and installed a drive shaft flange spacing Shims to bring the space to specs per the Barrington.



I tried with 4mm first, but I had a very hard time installing the rear trailing arm and the spacing came out of specs.



I had to remove the trailing arm and remove the drive shaft to install a 3mm spacer that worked for Zenaida.


I went for a ride and is shifting better then before, is amazing what 650ml of lub can do for your gears!