BSA Owners' Club Workshop Discussions

The BSA Workshop => Twins => Topic started by: Lurcher on 21 Apr, 2025, 15:41

Title: Fuel leaking into air filter
Post by: Lurcher on 21 Apr, 2025, 15:41
Hi all, having issue with my 1969 Royal Star.  Went out on her today, started fine 2nd kick from cold & went for a run of a few miles.  Stopped & could not get her to start again - left her for an hour, came back & she started fine.  Ran her around the block & once again having run could not get her to start. 
Started to look for the issue & found fuel dripping slowly from the air filter.  I'm not the greatest mechanic but suspect fuel is getting from the carb into the air filter & suspect float bowl issues - needle not seating properly maybe? 
Any advice would be much appreciated. 
Thanks.
Title: Re: Fuel leaking into air filter
Post by: iansoady on 21 Apr, 2025, 16:07
Your guess that it's the needle sounds spot on. I like the newer alloy ones with Viton tips, which are slightly dearer than the brass ones.
Title: Re: Fuel leaking into air filter
Post by: Lurcher on 21 Apr, 2025, 19:06
Thanks Ian, will get a new one with the Viton tip ordered.
Title: Re: Fuel leaking into air filter
Post by: BrummieJon on 23 Apr, 2025, 13:45
Poor hot starting sounds like a condenser failure
Title: Re: Fuel leaking into air filter
Post by: iansoady on 23 Apr, 2025, 14:18
I'd agree with a magneto but with a unit twin?
Title: Re: Fuel leaking into air filter
Post by: idie on 23 Apr, 2025, 17:08
If fitted with points. Yes
Title: Re: Fuel leaking into air filter
Post by: V500 on 23 Apr, 2025, 18:41
New one on me. On mags, yes, but I've never known it on coil-and-points cars or bikes.
Capacitor (condensor) failure is usually indicated by sparking/burning points.
Title: Re: Fuel leaking into air filter
Post by: DAVE BRADY on 23 Apr, 2025, 20:44
Hi Lurcher,

Was the bike running OK before this problem?
As mentioned, it is probably a float/float needle problem. When you stop and then the bike won't start again it is probably flooding. If you leave it with the fuel turned off then excess fuel will run out of the carb. and also evaporate. Hence, it will start unless you leave it with the fuel on and it floods again.

Dave.