The BSA A7-A10 Forum

Technical => Clutch, Primary, Gearbox => Topic started by: a101960 on 26.04. 2009 15:42

Title: First gear selection
Post by: a101960 on 26.04. 2009 15:42
Here is a little conundrum. I recently adjusted my rear chain and ever since doing so engagement of first gear when stationary is a bit erratic. Sometimes (usually when I am the head of a queue of traffic at for example traffic lights) I dab the gear lever and go to pull away only to find first has not engaged. Maybe I should explain that previously I could feel the gear engage whereas now there is no feel or detectable feed back from the gear lever. This only happens when the bike is stationary, when the bike is on the move it always goes into first without any problem. I have no trouble selecting neutral, and all the other gears engage without any problem. If I put the bike up on the centre stand I can select all gears (while spinning the rear wheel). Before adjusting the chain when engaging first while stationary there used be a clunk, and I could feel the gear engage. Could this be due to the chain being over tight? I have set the chain tension according to the BSA figure of 1 1/4" play. Any ideas about what might be going on here?
Title: Re: First gear selection
Post by: groily on 26.04. 2009 18:11
Seems weird but could well be the chain's too tight. 
Whatever the book says, I try to do mine so that with me sitting on it there's a good half inch of slack still available for suspension movement over bumps. That translates in my case to more like an inch and three quarters when the bike's on the centre stand. But then I'm, er, large, and doing the adjustment usually gives me a pain in the side as I'm not so constructed that I can eat my toes etc etc.
Always far better to have a bit too much slack than too little. Why not ease it off a bit and see what happens?
As an aside, I don't find BSA pre-unit rear chain adjustment one of the more satisfying aspects of ownership, I have to say. There seems to a lot of difference in tension between no-load and full-load - more than on many other machines - which is presumably down to the relative positions of g/box sprocket and swinging arm pivot (although they don't look to be further apart than many another machine of the era).
Title: Re: First gear selection
Post by: A10Boy on 26.04. 2009 18:27
Have you checked your primary chain tension? It could be that an over tight rear chain could twist the gearbox on its bolts.