BSA Owners' Club Workshop Discussions

The BSA Workshop => Twins => Topic started by: chrisx1 on 15 Jun, 2023, 13:43

Title: vapour lock
Post by: chrisx1 on 15 Jun, 2023, 13:43
I took the A65 out after fork and clutch rebuild. seemed to be running well for a short time, then it died. No fuel getting through. I removed the float bowl to find that the float had somehow come adrift, the steel peg it pivots on had come out of the groove. Put it back together and off I went, only to get the same distance again and it died again. removed the float bowl, everything was in place so reassembled it and off I went again, back home. Both times I couldn't get fuel through with the tickler.
Now I've read somewhere about fuel vapour lock. I have the insulating washer fitted between carb and manifold.
Anyone else had similar problems?
Title: Re: vapour lock
Post by: Allan G on 15 Jun, 2023, 14:20
Did you have a tank bag fitted or anything over the fuel cap? you can get vapour lock if you do... Strangely the few times that it has occurred to me have been on really hot days.
Title: Re: vapour lock
Post by: DAVE BRADY on 15 Jun, 2023, 16:39
Hi,

Check that the hole is clear even if not being visibly obstructed.  Even if you can blow through it there can be debris floating about that can move and block the hole.
My wife's A10 started to suffer from cutting out when slowing for junctions/traffic lights.  By the time we stopped and gave the carb a tickle it fired up as if no problem.  The hole in the filler cap seemed to be OK but on returning home I compared it to new one and the difference was surprising.  Although I could blow through it there was obviously still a periodic restriction due to loose internal corrosion.
A new filler cap solved the problem.

Dave.
Title: Re: vapour lock
Post by: chrisx1 on 16 Jun, 2023, 19:38
I think that was it. I found a small nail that was just the right size. Poked that into all three holes and I think that's sorted it. Fingers crossed.