ok guys i am new to bikes all togather so i just bought a 79 kx 125 it runs good somtimes when the cluch is in it cracks open like theres nothing to it but when under a load at mid to high rpm it likes to bogg out but somtimes it comes to life at high rpm and runs good also i was wondering how to tell when it needs a rebuild i hear a chatter in the motor not aknock just a chatter and if it needs it where to find the parts thanks