Thanks Norm and Nath for this advice; much clearer now. I did find a broken wire which was from seat switch to ground, and thought this was the smoking gun. but I think it had been broken all along as I was able to start and run the engine previously without being on the seat.
I guess for tuning etc you need to disconnect seat switch earth or you couldn't have it running without being on it. Tricky to get to the main jet screw when sitting on it.
I'll look at it again later today and report back.
Cheers and thanks again - what a great resource this is.
Doug
