I agree with Bill in that a cylinder/piston issue is a strong possibility. I had a Thomas snap off the screw that holds the top half of the piston to the conn rod. You could hear the racket over the engine noise of the Kawasaki mule while driving up. Maybe something on top of a piston also, that jams up the works at TDC....not much clearance in there.

Whatever the reason, dis-assembly is in order.

"Forget pounds and ounces, I'm figuring displacement!"

If we accept that: MBG(+)FGSF(=)HBG(F1)
And we surmise that: BG(>)HBG(F1) while GSF(<)HBG(F1)
Would it hold true that: HBG(F1)(+)AM500(x)q.d.(=)1.5lbGRWT?
PB answer: It depends.