BSA Owners' Club Forum

The BSA Workshop => Twins => Topic started by: LIONELSMITH on 06 March, 2017, 11:57:43

Title: A10 SRM Five gear custer
Post by: LIONELSMITH on 06 March, 2017, 11:57:43
I am in the process of rebuilding the engine on my A10. It needed a double rebore and the journals ground to twice a normal grind. As the engine had been left too long before a rebuild I am assuming the gearbox will need attention. The kickstart sometimes sticks, according to haynes that is the ratchet or quadrant. I have a new final drive sprocket and SRM anti drip sleeve nut. Both Haynes and the service sheet say I must remove the gearbox to change the sprocket, is this true? Also Has anyone had the SRM five gear cluster fitted, are the ratios any better?
Title: Re: A10 SRM Five gear custer
Post by: JulianS on 06 March, 2017, 12:15:32
The kickstart ratchet, its bush on mainshaft and quadrant do wear sometime to extreme. Only examination will tell.

The sprocket can be changed with box left in frame just need to lock it to undo the old nut and do up the new one with oil seal. That takes a 1 1/2 inch AF spanner. The only thing you cannot really do with box shell in frame is to replace the main bearing and layshaft end bearing.

Replace the existing oil seal whilst sprocket off. The current prodution ones dont fit exactly they are a fraction too large in diameter (about 0.5 mm) to fit snuggly in the bearing recess and you may have to gently ease it so it fits properly.

Title: Re: A10 SRM Five gear custer
Post by: STAR TWIN on 07 March, 2017, 14:21:07
The STD swinging arm BSA box has a bit of a gap between 2nd and 3rd gear. However, the A10 engine is sufficiently flexible and torquey that you really don't notice it. Try the normal 4 speed first before going to the expense of a 5 speed cluster.