I've owned two of them and both of them ran great with no problems. On the second one I even removed the stock muffler, placed it on my shoestring and modified a pitts for the OS 91 to fit the mounting holes on the .75, runs just great.

The theory of the o rings leaking thus not allowing the engine to shut down, is nothing but properly adjusting the low end needle. I had the same problem on my first engine it was just a matter of adjusting the low end correctly.

Blackie