R100GS gearbox endfloat

[tatters_2005]

Hi, l recently finished rebuilding the gearbox on my 1992 R100GS with new bearings/seals and HPN 1st/5th gear, after many attempts at working out the endfloat with a depth micrometer and shimming plate l cant get any were near the stated 0.05mm clearance as l keep getting different readings on the bearing outer races in different positions (3/9 O`clock etc) and am going to have to admit defeat.

Can anyone help me or know some one l can pay/send the box to so the endfloat can be set properly, l,m going off on a RTW trip starting this summer so quite paranoid about having no gearbox issues

 

[(RIP) Proff]

Paging Rob or Voyager

 

[Rob Farmer]

I always put the micrometer across the center race of the bearing and then measure down very close to the outer race. If you rock the micrometer you can tell if it's square on the inner race. Obviously if you have a small footprint micrometer you will struggle.

Don't be gentle knocking the bearings onto the shafts either. I have an old camping kettle filled with clean oil that I heat up on my camping stove, put the bearing in and leave for 10 minutes before scooping out and dropping onto the shaft. Then give them a good smacking with a tube the right size to fit onto the inner race.

The shims vary by huge amounts. I spent ages measuring them and putting them into marked bags showing the sizes (Tarka would be proud of me).

Shimming should be done this way:-

 

[Voyager]

l can't get anywhere near the stated 0.05mm clearance as l keep getting different readings on the bearing outer races in different positions (3/9 O`clock etc) and am going to have to admit defeat.

Can anyone help me or know some one l can pay/send the box to so the endfloat can be set properly, l,m going off on a RTW trip starting this summer so quite paranoid about having no gearbox issues

I haven't found a problem when measuring the bearings as they protrude through the shimming plate, but I have found variations when measuring the depth of the housings in the rear cover.

I usually take 6 or 8 readings then re-do the positions that are out of step with the others. When I finally get a series of readings that I can believe in I go with, or near, the shallow reading as thats where the shims will bear.

There is quite a lot of expansion as the box heats up and my re-built boxes are invariably tight when cold but OK when warm. They ease off after 1,000 miles or so.

Like Rob, I measure the shims, singly and in combination, as they can vary a lot, particularly if they have been used before. They are supposed to come in four sizes - 0.20mm, 0.28mm, 0.36mm & 0.50mm - but don't rely on it.

Oh yes . . I drilled my shimming plate so that it can be fastened down to the gearbox with the original end cover setscrews - with a new gasket underneath. That should ensure that it is level and the gasket is in its final position before measuring.

If it will help your paranoia, I'll build your gearbox for you - but that won't guarantee that the new quadrant/selector springs won't fail in some far away place

One day Bumpmuncher will get his bike back on the road and will be able to provide a critique on his box that I re-built.


Bob.

 

[Rob Farmer]

but I have found variations when measuring the depth of the housings in the rear cover.

I forgot to mention that. I don't think I've come across two the same depth.

 

[Voyager]

Tatters 2005 . . .

As a matter of interest, does your gearbox have a circlip in front of the front output shaft bearing - like this ????

BMW stopped fitting them some time around 1983 then re-introduced them around 1993 (it seems they don't publish details of the changes). Your '92 bike may have been modified in the past.

Some of us have modified the output shafts to take a circlip. It is supposed to prevent the front bearing being pushed forward on the shaft under load, pre-loading the front and rear bearings, and causing rapid failure of the bearings through axial load.

When I re-built 'Bumpmuncher's' box, the front bearing had moved at least 1mm on the shaft and the bearing was like a kid's rattle

If you are going to be putting a lot of load on the bike during your RTW tour I'd be inclined to carry out the mod if you don't have a circlip fitted already.

My local Engineering Works charges about £50 to grind a circlip groove in the shaft.

Happy to discuss

Bob.

 

[tatters_2005]

Cheers for the replys guys going to give the box another look next week other wise l,ll let you know voyager, also had the circlip mod done by a machinist.

not much rush at the moment waiting for my spare shaft to come back from HPMGUY on Advrider new polyurethane damper and greaseable U-joints.

 

[Voyager]

Cheers for the replys guys going to give the box another look next week other wise l,ll let you know voyager, also had the circlip mod done by a machinist.

not much rush at the moment waiting for my spare shaft to come back from HPMGUY on Advrider new polyurethane damper and greaseable U-joints.

It sounds as though you know more about this than I do

One hears reports of factory gearboxes being found to have the wrong shimming. I can't swear to always getting 0.05mm clearance, I just get as close as possible with the shims available - without making the clearance too tight.

(Confession time ).

Bob.