Gearbox rebuilder

[A10Boy]

Team

I have some wear on the clutch / gearbox mainshaft on an A10 which will need a gearbox rebuild shortly. Given that the gearbox has blind bushes which need fitting are reaming and will possibly need the shafts regrinding, and considering the safety aspects, I am considering sending it to a specialist for service or exchange. Does anyone know of a company or individual [apart from SRM] in the uk who can do this work ?

Much appreciated if you do.

[a101960]

Try this Guy.

J B Restorations BSA pre unit gearbox specialist.

Windy Hill
21A Ann Street
Dalton in Furness
LA15 8BG                Tel/Fax 01229 465635

John

[A10Boy]

John

Thanks for your quick response, I'll give them a call.

Andy

[lawnmowerman]

The PO of my bike had the gearbox rebuilt by JB - also the engine with roller bearing conversion. Haven't done too many miles since the rebuild but everything seems ok so far.

Jim

[A10Boy]

I am trying to weigh up whether I have just a bit of play or whether the gearbox bearing as about to fail. If I undo the primary case cap and move the primary chain up and down, it makes the slack in the rear chain move up/down by about 1.5mm. I know in theory this shouldn't happen and indicates wear in the box output bearing/sleeve interface, but is it excessive ? I would rather a gearbox rebuild be a winter project.

JB says it's extremely unlikely to be the bearing failing if the box works otherwise OK. Do any other members have play like this?

[brackenfel]

Hi Andy,
I'm just finishing a gearbox rebuild on my A10.. My shaft did not move, neither does the shaft in the spare box I bought to make a better one from the two.. Mine did not select 2nd & third well & the PO said (rightly for once) he thought that the layshaft bushes weren't good.

Although I bought 2 new bearings , layshaft bushes and all the bushes that fit in the outer and middle casings the only thing I didn't replace was the large outer bearing on the sprocket end of the mainshaft....!! Those bearings are big and I'd imagine would make quite a row if they were on the way out..
Are you sure the box itself is not loose in some way???

The shaft actually fits through a gear which in turn fits into the bearing behind which is the oil seal. The gear had to be persuaded back into the bearing, no way was it slack..The shaft just slides in nicely..

If it were mine I'd get the primary off so that you can really check what's going on before planning a box rebuild - mine has cost rather a lot so far...

Good luck,
Adrian

[A10Boy]

Thanks Adrian, good advice. I am planning to take it apart to see whats going on, but as you know thats the old story, you take it apart to look and find something then its a month off the road and 500 quid up the swanny.

The whole clutch / shaft / sprocket sleeve must be moving around, but the box is tight in the frame. I need to strip it to see, as you rightly say.

regards

[brackenfel]

Hi Andy,
Mine started with rough gear selection... The gearbox is partly assembled on a table beind me (tolerant wife!!) & I've had to buy a fair few parts on the way so I sympathise. Hopefully it'll all be worth it!

Hoping you find something straightforward to explain this.....

All the best,

Adrian

[brackenfel]

Andy,
Had a chat with a good friend who's had British bikes for decades including BSA B31's (same box) & he reckons it's not unknown for the bush inside the output gear to wear..

Maybe this is what has happened to yours, just thought I'd mention it...

Cheers,
Adrian