Hi , the bike was a private sale , its in good shape and has done 28k and was used intermitentely. After charging the battery overnight it started right up so the issue seems to be lower voltage- enough to crank , not enough to spark . I will monitor that battery with a voltmeter , it may well be past its best and need changeing . Also setting up a way to trickle charge the battery every time the bike is parked . I use heated clothing and it also has heated grips so the battery will get a tough life ... maybe I can wire two batteries in parallel as there looks to be room at the back of the seat for another ... certainly a cheaper solution if needed than the high capacity lithium batteries . Thanks for your advice
I've been using one of the smaller CTEK ones (XS0.8 I think) for a few years now with no problems:-