BSA Owners' Club Forum

The BSA Workshop => Singles => Topic started by: 6352N19-11 on 24 January, 2018, 09:50:36

Title: C15 misfires
Post by: 6352N19-11 on 24 January, 2018, 09:50:36
Hi
My C15 misfires at higher revs. have put the bike back together after 20 years. New wiring loom, new capacitor, new battery, new plug , new HT lead and refurbished carburettor. Started ok but would only run very fast with no misfire. exhaust pipe went red.
Dismantled and rebuilt distributor top end ensuring bob weights in place and working. Kick starts fine first time and idles ok, sometimes have to blip the throttle if cold to keep C15 running then it settles down to tickover. When I twist throttle at higher revs C15 starts to misfire and exhaust pipe goes red again.
have checked settings points and plugs.
Any help appreciated
Cheers
Richard
Title: Re: C15 misfires
Post by: AWJDThumper on 24 January, 2018, 10:08:38
The red exhaust is normally indicative of either a very weak mixture or a retarded ignition. I would double check the timing is correctly set and everything is ok with the auto advance. It sounds as though the carb should be ok but have you checked the carb settings and needle position? Have you still got the original air filter fitted - if not then this will slightly weaken the mixture but can be compensated with a slight increase in main jet size. If ignition and carb ok, you may need to think about the state of the engine. Was the top end of the engine overhauled including the valves? Are you 100% sure of the valve timing set up?
Title: Re: C15 misfires
Post by: C10 on 24 January, 2018, 10:58:20
AS AWJDThumper said.         or maybe a sticky valve, or settings not right somewhere
or maybe a valve is on its way out,once it gets hot not seating right??       pop the head off if all else is been checked..