problem with NR engine
 

Hi guys:

Last month I broke in a brand new novarossi engine using a break in bench. The first thing I did was shim the engine with a special gap tool, seting it up to 0.39 mm of head cleareance (the best value form the altitude of my city). The engine have never developed as my previous engines. To be very honest, the engine was terrible, poor top end and low torque. Yesterday I oppened up and the piston was tottaly black. I've never saw a piston like that. Is it predetonation or not? The compression is very good, it didn't seems to be worn out. My brother's engine is using the same setup and it has no problem after 1 galon of fuel.

regards

Eduardo