Carberetor type ?

[johnbrigg]

Hi. I have a 67 c15 fitted with the fss engine running the 626 amal concentric carb, which hasn't got choke fitted.
The bike  is difficult to start and then when does , doesn't run for log, which makes me think maybe carburation issues.
Does anyone know if this is the best carburetor for this engine or should i try a 375 /376 ?
Also if the 626 is correct, what jetting would be recommended?
Any thoughts would be appreciated
Many thanks John

[rhyatt]

I'm pretty sure the 376 is correct for the FSS, 1" bore.
Do look on the Burlen site in Salisbury, they're the experts on Amal

[Spaceman]

I assume this is basically an SS80 engine which would originally have had a 376 carb fitted. The 626 is ok for size and should probably have a similar main jet of 200 with needle jet of .106 and needle position 2. If the jetting is along these lines then carb performance can depend on its condition, especially as they wear out with time. It's worth checking the flatness of the choke flange and O-ring and it's worth checking whether the throttle slide is badly worn and no longer a snug fit in the carb bore. The latter in particular can lead to a weak mixture and difficulty in getting the engine started.

[leon bee]

Isn't this where the little idle jet in the concentric is clogged and needs cleaned out with #78 twist drill?

[neil1964]

Isn't this where the little idle jet in the concentric is clogged and needs cleaned out with #78 twist drill?

That is a really common and irritating problem and I can vouch for that!