BSA Owners' Club Workshop Discussions

The BSA Workshop => Twins => Topic started by: watts on 20 Jun, 2026, 17:07

Title: A65 Gearbox sprocket nut
Post by: watts on 20 Jun, 2026, 17:07
I am having trouble tightening the nut because I cannot hold the sprocket tight.
Am I missing something obvious or is there a simple solution.

The engine is on the bench.

Thank you.
Title: Re: A65 Gearbox sprocket nut
Post by: JJC on 20 Jun, 2026, 18:04
Not really!  The best way to get it tightened to the right torque is to do it in-situ with chain on and back brake applied, which of course means a partially disassembled engine in-situ..... and probably isn't a very helpful suggestion... The other option is to make some kind of holding system involving a length of chain that fits around the sprocket and is attached to some sort of lever to hold things while tightening. 
Title: Re: A65 Gearbox sprocket nut
Post by: cdsdorset on 21 Jun, 2026, 00:11
Jam a rag between the sprocket ans casing or the chain.
Title: Re: A65 Gearbox sprocket nut
Post by: DAVE BRADY on 21 Jun, 2026, 07:45
Hi,

As you have the engine on the bench, put the chain on the sprocket and put a screw driver though both runs of the chain just behind cases. Put a piece of wood in to protect the case.
As you turn the sprocket it will pull the screwdriver hard against the case and the sprocket can be tightened.

Dave.
Title: Re: A65 Gearbox sprocket nut
Post by: limeyrob on 21 Jun, 2026, 11:10
Yes, that's how I do it too.
Title: Re: A65 Gearbox sprocket nut
Post by: watts on 21 Jun, 2026, 22:32
Thank you for you suggestions.