BSA Owners' Club Workshop Discussions

The BSA Workshop => Singles => Topic started by: Singleton on 23 Jun, 2018, 21:45

Title: C15 gearbox
Post by: Singleton on 23 Jun, 2018, 21:45
Hi.
My C15  puts itself into gear when lent to the left hand side on the side stand.
Every time .
Any thoughts about the cause please.
Title: Re: C15 gearbox
Post by: JulianS on 23 Jun, 2018, 22:02
Incorrect assembly - missing parts - thrust washers - too much float on gears/shafts - worn bushes/bearings/shafts/pinions.

Broken springs - camplate spring?

Has the problem just started? Was it OK before you carried out some work?

Engine running or not?

Which gear engages?
Title: Re: C15 gearbox
Post by: AWJDThumper on 24 Jun, 2018, 08:05
The obvious explanation is that the leaf spring that holds the camplate that indexes the gears has broken or is damaged. The notch on the end of the camplate for neutral is very shallow compared with the other gear positions and it doesn't take that much force for the camplate to rotate from this shallow notch to the deeper notches for 1st or 2nd gears. That said, it's difficult to see how sufficient force could be generated to cause this to happen by tilting the bike on to the sidestand. Unfortunately, the only way of getting to the bottom of the problem and fixing will probably be to take the gearbox apart.
Title: Re: C15 gearbox
Post by: Singleton on 24 Jun, 2018, 09:06
Thank you both.
Time to open her up again and find the problem.
The leaf spring could be the original so maybe a good time to renew also the thrust washers to ensure they are correct.
I 'll let you know. Thanks again
Title: Re: C15 gearbox
Post by: AdrianS on 24 Jun, 2018, 11:16
I thought the gearbox drops into top gear if that index spring breaks.
When I had one go many years ago Fred Hanks told me to put 2 in when replacing!
If I remember it didn't take too long to get the gear cluster out and replace the springs. Can't see what else would cause the gearbox to put itself into gear other than a weak or broken spring.