I think you are definitely on the right track,but i have a feeling it’s a wiring/ignition problem.No bother charging(in the shed,anyway),steady 12-13.6v through the rev range.Need to buy a more powerful charger,my optimate wont revive my flattened battery,and its impeding progress!Did start off sounding like a fuelling fault,but i(hope i have)all but ruled it out now.Thanks to all who took the time to reply,appreciated.
I gave up! Previous owner bought it back,he’s an excellent custom bike builder,so it’s going to be getting some serious modifications.
Thanks to everyone who replied with advice,the cash from the sale is going towards goodies for my LM3.