gearbox sprocket lock washer

[bonny]

i have just bought a new 21 tooth gearbox sprocket for the a10, i went to fit it and found that the sprocket doesn't leave enough room on the splines to fit a lock washer. anyone know a solution ? the sprocket is british made and looks to be great quality.

[beezermacc]

Have you tried tightening the nut without the washer, this might draw the sleeve gear through the bearing. If the gearbox is newly assembled maybe the sleeve gear wasn't pushed all the way home. If this fails I would suspect the sprocket is marginally too thick. Have you got an original one you can measure against?

[bonny]

I'll try that beezermacc, but i have a suspicion that the dreaded pattern parts monster strikes again.

[bonny]

tried to draw out the sleeve gear with the nut and nothing , i have a feeling the gearbox maybe a b31/33 unit  , the edge of the sleeve gear is about 2mm beneath the face of the sprocket. 

[trevinoz]

Bonny,
               B31/33 gearbox is the same as A7/10.
Trev.

[bonny]

Bonny,
               B31/33 gearbox is the same as A7/10.
Trev.

thanks again trevinoz, but isn't there some differences due to offset or is that the engine plates i am thinking of ?

[trevinoz]

Bonny,
              Probably you are thinking of engine plate sets.
The boxes are exactly the same. Just different sprockets.

 Trev.

[chaterlea25]

Hi Bonny,
Has the sleeve gear moved back into the gear box a little??
It may have moved in when you pushed on the sprocket
Engage top gear that should hold it out against the bearing
HTH
John O R

[Brian]

I would check the new sprocket against the old one. I had this same problem a few months ago with a new sprocket I bought for a B31.

The one I had was about 3mm too "thick". The section the seal runs on was too wide and I had to machine the sprocket to the original dimensions. Like yours there was not enough thread protuding for the nut to go on plus the chain alignment was abour 3mm (half the width of the teeth) out of line.

I suppose a new sprocket that can be altered to suit is better than no sprocket but sometimes these aftermarket parts really p##s you off.

[bonny]

thanks all , i don't have an old sprocket to check it against , i have already thought of turning the sprocket down a bit, i'll look at it again tomorrow. is there anywhere i could get a drawing of a sprocket ?   

[bonny]

i found an old gearbox sprocket today and tried it, exactly the same as the new one, it sits 2 or 3 mm above the splines so there is nowhere for the lock washer to sit. i also decided to check the gearbox out as i never bothered to open it before, i found the third gear mainshaft pinion (17 tooth) was missing a dog, and the thrust washer that sits between the second and bottom gear pinions on the layshaft to be missing. no wonder i couldn't get the thing to engage gears.also the selector fork has one end that appears to be flattened or worn down , is this the correct shape or is it worn out ? where can i get replacements of decent quality ? the rest of the box is in great condition.   

[muskrat]

G'day Bonny,
                 yep selector plate shot. Doesn't look like much room between back of sprocket and g/box case so it must be the sleeve gear not all the way home. I had a gear do that in the A65 two weeks ago.
Looks like it's a box rebuild.
Cheers

[beezermacc]

Don't forget that the gearbox sprocket has a dished centre so the problem may lie in the depth of the dish rather than the overall thickness, i.e. if the dish was a bit deeper the tab washer would fit. As you've got the box stripped down you can assemble the sleeve gear, bearing, seal and sprocket prior to full assembly to check that issue alone.

[bonny]

G'day Bonny,
                 yep selector plate shot. Doesn't look like much room between back of sprocket and g/box case so it must be the sleeve gear not all the way home. I had a gear do that in the A65 two weeks ago.
Looks like it's a box rebuild.
Cheers

I had a feeling the selector plate was knackered , no big deal, one concern i have is the gearbox is stamped tri T, i know this means trials torrington ,it does have the torrington needle rollers in the cases , but has anyone ever ridden a solo a10 with a trials box ? I have a feeling the bike was pulling a chair at some stage , would this account for it ? Surely no sane human has ridden an a10 in trials ?

[chaterlea25]

HI Ronan,
I have a friend who is collecting a job lot of gearboxes tomorrow (Monday)
I am going to build some gearboxes for him
He is also building a Trials Goldie and I think he would bite your hand off for a trials box ????
I have some spare gears and bits I dont have a selector claw though
Send me a pm and we can discuss details of how to get your gearbox sorted
Regards
John O R