The final item on rebuilding my A10 was to fit the reconditioned magneto. To set the timing I put it in gear, turned the back wheel to set correct piston position - all ok. However problem when I came to take it out of gear - lever moved up and down but gears would not change even when turning the back wheel and hence gearbox shafts.
Removed outer and inner gearbox covers to see what was stuck. Both mainshaft and layshaft turn ok but the selector quadrant appears to be jammed in 4th gear and I cannot get it to move.
To strip the box any further I need to get the quadrant support shaft out but this is secured by a grub screw at the back of the gearbox which is inaccessible with the box in the frame. Don't want to remove the box as that means removing the engine as well!!!!!
Anybody got any bright ideas about what could be causing the problem and also whether it is possible to strip an A10 box without removing it from the bike.
:) :) :) :)
Just a thought:- If the lever moves up and down but the quadrant isn't moving, to me it would suggest that the gearlever isn't properly tight on the spline. That could be either the spline or the lever. If you've already checked that then I guess thats the limit of my help.
Mike 8) 8) 8) 8)
Thanks for the suggestion Mike, unfortunately it's nothing as simple as that
With the clutch off the box can be stripped almost completely leaving the case in the frame and the large ball race in the case.
Easiest to leave the mainshaft attached to the inner cover.
The grub screw is just accessible but tight. See a previous post.
https://www.bsaownersclub.co.uk/bsaoc_forum/index.php?topic=1039.0
Thanks for that Julian. I'll have to spuddle in my screwdriver box to find one that I can get in with - always assuming my hands will fit into the available space. But if it's been done before then at least I know it's possible
Just looking at the photo you posted on the other thread Julian. Is this taken with the primary chaincase in place or has the clutch and PC been stripped off?
All primary drive removed you cannot strip the box with clutch still on.
Hi,
Is it possible that the sprung plunger that holds the selector plate has jammed or set too tight? Also were the gears indexed on assembly?
Worth checking the plunger before stripping as I think it can be accessed from underneath.
Dave.
Thanks Dave. That had crossed my mind so that could be the job for today. Part of the problem is that because it's in gear and the primary drive is connected you can't turn the gearbox without turning the engine which makes it hard work. I may disconnect the primary chain so at least the gear box will turn easily which may allow the quadrant to move and change gears. Regarding indexing - I was aware of this when I put it together and certainly thought I got it right.
Hi,
I am sure you must have tried this but pull the clutch lever in and the rear wheel/gearbox should rotate.
Dave.
The only problem with that is that I then need 4 pairs of hands while standing in three different places - 1 for the clutch, 1 for the back wheel and two to manipulate the gear box. I think I'm going to have to bite the bullet and do some dismantling. It's probably worse now that I've taken the covers off as the the indexing on the selector fork has been lost so the whole lot needs setting up again.
OK,
One last suggestion. Stand as if going to start the bike standing on the right hand side. Pull in the clutch lever and turn the kick start. The gearbox and rear wheel will rotate. This may be enough to un jam anything that is stuck. Turn everything a few times and then see if the gears can be moved.
Perhaps try a strong cable tie on the clutch lever so that you can be free to fiddle with the gear lever as you turn the engine as sometimes things a re more likely to free when being moved.
Straw clutching but it might work.
Good luck.
Dave.
Hi,
Obviously you have taken the kickstart off already but holding the clutch lever in with cable ties should still help.
Dave.
Hi Dave
Thanks for thinking about it. Problem is I have taken the covers off and the clutch operating mechanism is in the outer casing. I have managed to get the camplate moving and turning the back wheel at the same time but because there is no cover it won't change gear because the shafts have nothing to push against. Putting the covers back on with the indexing wrong may just jam it up more.
Time for a cup of tea and sandwich and a long think.
It sounds as if the selector shaft pins were not located properly in the tracks on the cam.
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.
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
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
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
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).
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
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.
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.
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!!
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.
That sounds great news. Glad you've got it sorted.
I'm still doing mine!