Hey showstringracer, I started the thread about the backfire on my OS Surpass II a few days ago and never got this much information! I have read this all today but Before reading this today I took my plane to the field and leaned the high end a bit from information given to me from my post and it did NOT backfire although all the while not trusting it at any time. My first backfire with this motor sent an APC prop and spinner flying, the prop hit a steel post behind the plane breaking it in two sending one piece at a fellow modeler hitting him in the hat/head just above the bill about 1/2" cutting him but luckly not badly, The hat saved him from a worse cut I am sure. But even though my motor did not backfire I traided it to another modeler before leaving the field. I personally think this OS Surpass II with Pump(oldversion of unknown date)should make a fine paper weight!
The information learned from everyone here I appricate and will use it on other 4-strokes but never will I own that one again. Thank you all for your answers and your help. Mike