I have a 1999 yz400f. The bike still runs but it is acting funny . If i was to go out to the bike i could push the kicker down as many times as i wanted,sometimes it will start and sometimes it takes 30 kicks to get the beast fired up , but sometimes the kicker will be stiff and you have to use the correct starting procedure . I just got the valves done thinking that that would solve the problem....it didnt . I am now thinking it could be the rings ..............please tell me what you guys think. ALSO......if i went to a 03yz450 would it be a huge diff?..Just now getting into jumping and racing.