carbs

[David Stepney]

I appreciate this may be a 'long shot', but have you got the right jets in the carburettor? For a Big Seven, they should be:- Main Jet 90, Compensation Jet 50, Slow Running Jet 60.

I would also restore it to electro-mechanical (points and condenser) ignition. I don't trust all this modern "electrickery". Electronics can fail in some really esoteric ways and often a buggered circuit board looks exactly like a working one!