speedfight 2 100cc 55 plate wont start?

basically i had just had it serviced and new rollers, and it seemed to be running fine, next day i gone to take it down the by-pass going about 60 and the engine cut out and hasn't started since, oil, fuel is fine just but a new starter motor in and cleaned up the spark plug, but it still wont start, it ticks over but nothing else, any help please?