You know, it was the first thing I looked for, but it was simply not visible, even with the spark arrester removed - I assume that is what the thing which screws over the hole is.
The litle blighter built it right up inside.
I must say what a lovely bit of engineering the carby is. And I imagine performance could be inproved even more by reducing the surplus thread on the screws holding the butterflies for choke and throttle - or even going to countersunk screw heads.
Doug
