Went out on the bike with an extra condesorbetween the cut out wire and earth as suggested by eddie, did about 20 miles though never went far from home, bike ran fairly well apart from occassional infrequent missfire, didn't stop engine till I got home, then bike restarted easily so stopped and disconneted extra capacitor and it was impossible to start so resconnected capacitor and bike started easily, so it definatly seems to be capacitorwill leave on for now until I decide what route to go down, either a rebuild or an easy cap condensor, probably the latter. just for cost.
think the mag is a lucas mn2 never paid much attention to it apart from drying points out not long after bI got it andchecking timing.
thanks to all for your help