A10 gearbox not selecting

[Pete A10]

Thanks for the suggestion. I think I'm into a full gearbox strip to sort out the issue. Just means a lot of other stripping out as well which is disappointing as I thought I had completed the project. Hey ho that's the way it goes.

[Saltydog42]

I hope you have fixed this by now but if not you can rebuild box in the frame but you can also remove the box whilst still leaving engine in place,
I have now done this twice, you have to rmove all primary drive side and support engine underneath as well as leaving front and head steady bolted up.
Remove rear bolts and timing side gearbox/engine plates to wiggle it out.
needs lots of tea and take your time
Good luck

[Pete A10]

Thanks for that.
I left it alone before Christmas and will hopefully have a go at it in the next couple of days.
Good to know as it will be easier to rebuild the box and get things lined up properly on the bench rather than crouching down on the floor.
I'll let everyone know in a week or so. Either successful or lots of bits lying around the garage

[MJM_58SR]

Hi Pete
I have been rebuilding my A10 gearbox and have encountered similar problems. Julian was an absolute wealth of knowledge as I've been doing it.
I'm no expert at all on these things but my gearbox was locking up and not changing gear etc. I stripped it loads of times on the bench.
The problem I had was I had changed the fixed pinions in the mainshaft and layshaft and they weren't fully home, as soon as I gave them a little press they popped on and although I haven't fully assembled it again I have tried both shafts with gears and they all rotate properly when casings bolted up.
I am sure the gearbox can be tested through the gears on the bench if you grip it in a vice or something g to hold it steady.
There are a couple of good articles that I read about rebuilding the box.
Hope you manage to get it sorted

[Pete A10]

I started stripping everything down today so should have the gear box off tomorrow.
Useful to hear about the pinion fitting. I fitted a new layshaft when I originally rebuilt the box so that's another possibility. Everything rotates ok, even when all the covers are on it's just the selection that seems to be a problem. Having now pulled the clutch pressure plate off I can more easily rotate the back wheel. The cam plate has un-jammed but by hand I can only move the plate to 2 different positions rather than the 5 you'd expect though this may be because I can't get sufficient leverage on the edge of the plate. I'll keep going and get there in the end (it's only taken me 2 years of rebuild to get to here so another couple of weeks won't be too bad).

[MJM_58SR]

The other thing I noted was that one of the selector forks wasn't seated properly on the edges of the gears so they couldn't move freely with the cam plate. You can see this through the inspection plate hole.
There are other things I have learnt from Julian such as correct thrust washer fitting.
If you have totally dismantled the gearbox and replaced parts then I would say if it's anything like me you will have something not quite right so be worth going through it all again and rest before fitting.
Like I said previously I'm not an expert

[idie]

If the cam plate is difficult to turn maybe you have the plunger done up to tight. Slacken it off so that you can turn the cam easily. You can always reset it later.

[DAVE BRADY]

Hi,

If you have gearbox apart then it is easier to check the function of the plunger in its housing and I think the workshop manual gives number of visible threads on the plunger housing as a guide. I believe it is 2 turns visible after the locknut is in place.

Dave.

[Pete A10]

Thanks Dave,
I think the 2 threads on the plunger is right. I know when I put it together before I thought it seemed too tight at 2 threads and actually set it at 4 threads. Maybe the plunger is too loose? I suppose if there is wear on the pivot then being too loose could cause it not to align properly. I'll get a better idea when the box is fully off the bike. Its amazing what you have to strip off in order to get at the bit you want - I've ended up with almost as many boxes of bits as when I started the project!!

[Pete A10]

Well, gearbox off, stripped and rebuilt and all the gears are now selecting. I did find that I had the camplate spring set at 8 threads out rather than 2 so the that may have been too slack. Also found that the selector claw was fitted 1 tooth off where it should have been so the indexing would have been off. And I thought I'd been so careful when I rebuilt it before!!!! So much for my mechanical skills!!!
At least I've learnt that you can get the gearbox off without removing the engine.
Gearbox is now refitted so I've just got to rebuild everything else I took off. Should be finished tomorrow.

[MJM_58SR]

That sounds great news. Glad you've got it sorted.
I'm still doing mine!