Hey people.. Time to scratch your heads for me. I could use some help here.. I was breaking in a new motor and when I was half way through my second tank it developed a nasty vibration. It occurs mid rpm range.. I have checked everything I could think off. Such as carb , head gasket & bolts , gas/ oil mix , mounting brackets/bolts and so on.. My hunch here is it could of just been a lemon from the get go.. It seem to be coming directly from the motor. It acts like a burnt valve but not seized up .. I'm going to wait a few days to see if anyone can help me trouble shoot this before I tear the motor down... Thanks in advanced!