Generac Dropped a Valve and Punched a Hole in the Piston - Will It Run and Make Power Again?

"This Generac GP6500 Generator was given away for free. According to the owner, she was running it when it abruptly shut down and locked up. A friend took it apart and discovered a valve dropped out of the head and fell into the cylinder punching a hole in the piston and destroying the head. This machine was given away for parts. Can it be rebuilt? Or should I just swap out the engine? Things were going well with the repair until the load test.

Generator Model: G0076700

I no longer use Harbor Freight Super Heavy Duty Degreaser in my ultrasonic cleaner. Harbor Freight changed the recipe. The bottle previously stated ""NON-CORROSIVE"". Now it says ""CORROSIVE"", ""do not user on Aluminum"". It now damages most carburetors. Recently I have been using Simple Green PRO HD with good results."