had a few days away from sorting the bike out following the bang noise on start up.
made a list of tasks to carry out before trying to start, but after turning over by hand at rotor ( ran freely, no noises etc ) put the bike on jumper pack and it wanted to start.
i was happy with this as my goal was not to start it at that point but to check the starter etc for fouling. i did not bother with the non starting checks as i was planning on doing so after checking the timing was fine etc (k4 fixed timing).
thought whilst chatting next to bike to check fuel amount ( i have a leaking fuel cap a lot of water had got in after our flash flooding in london. il get some fresh fuel in the morning and empty the tank and clean the plugs anyway, i will seal the fuel cap when the tank gets emptied and check online for the other rubber washer for the bit that opens. worst way a smear of LSX should fix the problem....
popping to suzuki in morning to collect a spring
in summary of the initial issues the bang was likely to be a false neutral and not quite in gear