Ruining them IS the fun.

Anybody who start grinding on a motor KNOWS there is a risk of popping it. But you accept that fact up front and forge ahead anyway.

I've popped a Ryobi conversion engine by turning it at almost 9000RPM. It lasted about 2hrs of run time before it exploded in the air. It's a disposable engine that you can buy for under $50 brand new. You can dig them out of trash cans for FREE.

Even a $60 glow engine is pretty cheap when you think about the total cost of this hobby. Grind on it until you've either burned it up or turned it into a paperweight. It's fun!!