Hi there
I went to Russell motors today. Well cool. Like going back in time and stuff. Good freindly and helpful there too. That les guy was there. Got loads of bits.

Unfortunately they have no more gearbox holder back/adjuster eye bolt thingys left.

Is it the sole purpose of the thing to drag the gearbox back and forth? Or does it act as a strengthening strut to stop the gearbox being wrenched forwards with the thrust of the engine.

Because if it's the former I may as well not bother with it. Has anyone been going about without one?

email (option): hutman80@hotmail.com

As I understand it, I used it to adjust the chains.

email (option): unpob@yahoo.com

Yea, I could adjust the chains with a rubber mallet
If that is the sole perpose of the adjuster, one could ride around without one?

email (option): hutman80@hotmail.com

Hi Maxwell, The gearbox can move about under the loads applied to it by the transmission chains etc., particularly if the threads on the gearbox mounting bolts are a bit worn and don't allow you to really tighten it up. Usually they seem to move backwards in the frame, tightening the primary chain and loosening the rear.
The gearbox adjuster if correctly set up can limit this tendency.
I tend to 'beef up' the gearbox bolts, nuts and locking plates (the heavy washers under the nuts).
Firstly I use the serrated locking plates from a swinging arm BSA (B31, A10 etc.) These are thicker than the originals and have a heavy serration on the back face which grips well against the gearbox plates.
Standard these come with a 5/16" hole through them which needs to be opened out to 3/8" to suit the M20.
Next I make wider nuts...about 50% thicker than a standard nut. Then longer than standard mounting bolts to suit. This allows you to 'swing' on the spanner a bit more without stripping the threads and exert a bit more pressure.
Its a bit of hassle making all the parts but worth it...Ian

email (option): ian@wright52.plus.com

oh toss, based on that information I should be sourcing some more bits and bobs then. (my gearbox bolts are a bit of a mish mash of od bits)

email (option): hutman80@hotmail.com

Hi Maxwell, I think many would regard my approach as OTT..but it's the way I do things.
At the very least get a good condition set of original components or well made replicas..even if you have to commission them yourself...Ian

email (option): ian@wright52.plus.com

I like the way the pre 49 b series box has it's adjuster, one bolt thing smack bang in the centre rear of the gearbox, hooked onto the frame.

The on the side method seems a bit less effective like.

nice one

email (option): hutman80@hotmail.com

The 46 XB31 has same through the frame bolt, but often that bolt can no longer be removed from the Alum in the gearbox due to corrosion effects from being located at the bottom of the bike. Lots of broken studs to be drilled out.

email (option): unpob@yahoo.com

you used to be able to get hold of stud remover/drill it a hollow drill that fits over the stud and cut down the edge of the stud taken the minimum of the hole

email (option): roger.beck@node6.com