A10 gearbox not selecting

[Pete A10]

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.

[Mike Farmer]

 

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

[Pete A10]

Thanks for the suggestion Mike, unfortunately it's nothing as simple as that

[JulianS]

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

[Pete A10]

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

[Pete A10]

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?

[JulianS]

All primary drive removed you cannot strip the box with clutch still on.

[DAVE BRADY]

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.   

[Pete A10]

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.

[DAVE BRADY]

Hi,

I am sure you must have tried this but pull the clutch lever in and the rear wheel/gearbox should rotate. 

Dave.

[Pete A10]

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.

[DAVE BRADY]

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. 

[DAVE BRADY]

Hi,

Obviously you have taken the kickstart off already but holding the clutch lever in with cable ties should still help.

Dave.

[Pete A10]

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.

[idie]

It sounds as if the selector shaft pins were not located properly in the tracks on the cam.