After messing about for hours trying to get the E50 to run and idle and fixing numerous air leaks. I decided to disassemble it to find the source if the problem. The first thing i noticed when i removed the flywheel was that it had been rubbing on the lighting coil and cut through some of its windings. Im pretty sure this wouldn't stop the bike running but i will investigate further. Secondly i discovered that slot in the flywheel that accepts the keyway on the crankshaft has been elongated which may well have affected to timing. Looks like a new lighting coil and flywheel is needed.