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Inner gearbox cover

Hello Everyone,

I have a bsa M20 spare gearbox and want to rebuild it. The inner cover is missing a piece where the bearing is placed, but on which the bearing does not rest. I have a question: can I use this cover without any problems or do I have to look for another one? Thinking e.g. to the oil level inside the gearbox ....? I hope someone has an answer for this problem.

Thank so far,




email (option): Vplrn AT

Re: Inner gearbox cover

Hi Andre, cannot see the pictures but think i know what you mean as this piece is often broken out or cracked.

Do not think it is a problem, it will not affect the oil level as there is a oil hole in the inner cover also.

It breaks out is when the mainshaft is forced inwards, maybe by hammering on the clutch or a fall of the bike where the footrest is bend into the primary chainchase and hits the clutch ???

The small ballbearing in the inner cover is only a light fit and will shift easily after which the 1st gear will touch the cover and breaks out this piece.

In the postwar box they tackled this by adding a circlip which keeps the small bearing in place.

BR Michiel

Re: Inner gearbox cover

Hi Andre, as long as the retaining washer 24-4236 that goes behind the bearing is held in place by what is left of the cover, all should be OK. The retainer is necessary (along with all the components) to maintain end float on the main shaft. Oil is not an issue as oil already flows from the inner case to the outer case via the hole on the right hand side of your photo above your letter "N".

Oops! Michiel beat me to it.

Re: Inner gearbox cover

I want to thank you both for the answer! I can start to build the gearbox.



email (option): Vplrn AT

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