Gearbox rebuild time - some questions....

[t20racerman]

Hi all
My A10 has been jumping out of 2nd gear, when under load and getting the revs going, for some time now. Decided to strip the gearbox down, and it wasn't a pretty sight. The layshaft was a 'tad' worn...



The bushes were badly worn too (and I mean BADLY!), as were (surprise, surprise...) the dogs on the 2nd gear. So, rebuild time it is. I looked on eBay and there was a guy selling FOUR complete sets of A10 gear clusters, all looking in reasonable nick, so I bid on, and won two complete gearboxes - (I'll use the best and sell the other on). So, before I get going on a rebuild, a few questions come to mind.

 - When fitting the bushes, is the end float of the layshaft fixed by the (hopefully correctly made) bushes, or is machining/shimming needed? What should the end float be? Actually, are the bushes for sale in the UK (eg at feked, Draganfly etc) good quality ones?

 - Can I replace the bushes with RR2T type needle rollers? If so, do I need to add shims, spacers etc. Has anyone done this with a standard gearbox?

 - Are there any other things to watch out for, or advice in general that might be useful? Although it all looks pretty simple enough to do, always useful to receive wise words (I'm a competent mechanic of many years experience, and have owned this bike since '83, just never done this particular job before)

Thanks
Adrian

[JulianS]

Fitting RRT needle rollers - the RRT layshaft journals do not have a scroll. You can get the closed needle roller in the main case, but not the core plug as it does not have a counter bore, though I dont suppose you really need a core plug with a closed bearing.

The  sandwich case bush bore is much too small for the needle roller and would need to be bored to size. The needle roller layshaft takes thrust washers at each end.

There was a standard box with needle rollers - marked STDT. It used a different layshaft (as mentioned above) and 3 of the original pinions were slightly different - the A and B gears are slightly wider and H is shown as a different part number but I cannot see any  visual difference.

Photo shows needle roller layshaft with its A pinion and thrust washer on left and the slightly narrower A from bushed box on right.

[t20racerman]

Ok, thanks for that - seems the RR2T idea is a no-goer then. It was just something I thought might be worth a try - but clearly far too complicated to bother with on a std cluster. :-)

[chaterlea25]

Hi T20,
An indepth thread on BSA gearboxes on Britbike forum by Magnetoman

http://www.britbike.com/forums/ubbthreads.php/topics/761770/15

John

[t20racerman]

Hi T20,
An indepth thread on BSA gearboxes on Britbike forum by Magnetoman

http://www.britbike.com/forums/ubbthreads.php/topics/761770/15

John

Thats brilliant - exactly what I was after. Thanks so much