speedfight 2?

adam bike doctor can you plz help as i,m at the end of my teather ive got a speedfight 2 i have trouble with is starting ive replaced the jets in the carb and it started fine so i turned it bk of then it wont start again it can run fine for a few days then it wont start again after that checked the battery its had new pistons and head theres no blockage spark pluga fine so i dont know what to do plz plz plz can you help thankyou