I am having tuning challenges with my .21 Nova Keep-On; in fact I've killed the original piston liner after 1 race and just ran in the replacement.

Engine behaves very strangly : it pulls well from low to mid but doesn't rev out after that. It's as though the engine is experiencing fuel starvation. Tried richening it but still the same, until it was obviously too rich. Engine runs very hot 130 degrees C.

There is very fine pitting on the piston surface and top plate. I think it's pre-detonation. But I am using stock shimming ( 2 silver and 1 copper - measured head clearance 0.6mm) and stock No.8 Nova plug. 25% nitro and 9% oil.

It's not the fuel tank nor the fuel line as my other engines were working fine.

Needle setting : HSN flush, LSN 0.3mm in, MSN flush

Any suggestions ?

Cheers