Strange carb(?) issue causing bike to stall

Started by Fellwalker, August 25, 2026, 08:17:17 PM

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Thomas

Hi Thomas,

  • The leaning bike - I always have the same effect with my C11 but never with the Sunbeam. it's the fuel level in the float chamber that changes with the tilt and has an effect on the slow running/air correction jet. A weaker mix is likely to speed up the engine (as it does just as you are about to run out of fuel).
  • I also had a back spitting carb. The reason was an imperfect ignition timing.


Cheers, Thomas
1946 BSA C11
1937 Sunbeam Model 9
... and a scratched Hyundai
(MSCR member)

Fellwalker

It's an Amal 276 and the float's on the left side.  I've just discovered that the throttle adjuster nut on the top of the carb is loose.  Having done it up, the bike seems to start promptly and seems more willing to tick over.  Will see if there's a genuine improvement tomorrow before I claim any kind of victory!

singleminded

What Model Amal carb do you have Thomas,and which side of the carb is the float chamber on.
John

Fellwalker

I've had some problems getting my Model 8 to start and then tick over, but following the Amal iterative adjustment process of adjusting throttle stop and pilot jet has got me to a point where the bike starts reasonably well and will tick over.  I then have two further issues:

1. If I lean the bike over to the left to put it on its side stand the tickover begins to slow and then the bike stalls.  I can't figure out what might cause this.  Could it be the float is set too low and I'm suffering fuel starvation?  Could the float be jamming when at an angle?  Debris in the carb?  Any ideas?

2. When riding along I'm getting quite regular spit back through the carb and I think the engine would stall if the bike's momentum didn't immediately restart it.  Reading the Amal tuning guide, could this be because the main jet is too high or too low?

Any insights welcomed!