hey,my name is josh.i have just bought a 07 Yz 125,my first 2-stroke.with a new plug the bike runs fine for 15-20 mins then starts to run crappy at lower RPM, then dies.then she will not go again.i will put in a new plug and then she will be fine and then it all happens over again.is it my rideing style or is it someing with my bike?..and i am trying to keep the RPM up high to.