I have a WS9 engine that I’ve just broken in. I’m about 3/4 a gallon through it now. Used the heat cycle method and kept it rich. Only just started really trying to open her up.

I added a shim to the head, so it now has 3 copper RB shims totalling .4, because I run 30% nitro.

I’m running OS P3 plugs.

The problem is, to get the engine to perform at high revs I need to lean it out to the point that it stops smoking at high revs and starts running hot (260F). Otherwise it’s too rich and boggy, never really screams like I’m told it should.

This is my first RB engine and I don’t want to run it too hot because I’m told they should go nuts and run on the rich side. Should I pull the extra shim out and drop the nitro to 25%? Or do I just need to wait until it’s had more fuel through it?