High RPM pops thur the exhaust
 

I had my 1/8 scale out today and it was not running like it should at high rpm it started to pop thur ex. I put in a new plug but no change so when I got back home I set everything back to ther factory settings and it still did it any thoughts on this issue thanks

Pre-detonation, i run 33% nitro and have the same problem from time to time, richen it up a slight amount and the problem will either get slightly better or go away completly. Of course you will not have all the power you are used to but you dont have to worry about damaging your engine. Other solutions are to A: Lower your nitro % B: stick another shim under your cooling head to lower compression ratio.