So I just purchased a warrior 350 with the big stroke crank done to it the guy before me let his friend ride it and blew it up he said you could hear him back on the trails flying probably about 4th gear then the motor slowly wind down like he applied the clutch then all of a sudden it sounded like he dropped it to 1st gear and it poped the chain off and started grinding in the motor now it won't fire and with it in gear and the back wheels off the ground you can not spin the wheels anyone have and ideal what to look at first as I am a car mechanic not a atv mechanic?