thanks for tips,havent removed tank,dont know how clean it is in there,bike is 50 years old,and been stood in a collection for years in america,when i checked fuel level with a torch did seem to have a orange sort of rust colour on petrol surface,have fitted a inline fuel filter to help if tank is the problem but still having starting problems.

Video if possible could help just to hear how the problem shows up. Does it sound erratic like spark or a starvation fade out but still trying sound.
Doubt its timing & as you say it would be all the time, but be sure you have gap at the points at least.

thanks for your interest,got bike working now,found out throttle valve was sticking which caused bike to rev at over 6000 rpm,stripped id down again got throttle valve to shut off properly,ticking over nicely at about 1100 rpm,waiting for weather to change so i can take it out for a test run,will let you know shortley how i got on.

Hi and welcome to the site. Is the fuel tap clean?
Also,the fuel pipe could be dissintigrating internally if it's been stood. I have experienced this twice.
If you're not doing all ready run E5 and fuel stabalizer.
Pete RT1 had a similar problem. The bike would just cut out. He rechecked the timing and reset the points.

thanks for your tips,fitted new fuel pipe and inline filter,have gone back to e5 petrol having been told to use e10,sorted out sticking throttle valve,bike running and starting better than ever,thanks to all who gave me advice.