I have a '97 F3 with 15000 miles on it. lately its been kind of "bucking" when I get on it in first. Just put a new chain put on before getting it out this year. Doesn't seem to do it if im just getting up to speed but as soon as I try to give it some gas it'll buck like 4 or 5 times before getting into 2nd. Any suggestions besides a rebuild??