Engine Tuning

[a6m2-n]

I have am currently getting a K&B .40 ready for flight. It seems to be getting enough fuel, and its throttle resposne is great, the starting is a little inconsistant, but i'm not worried because it is barely broken in yet. My question is should there be smoke coming out of the muffler? I seem to have none, but i read that this could mean it is too lean. What does it mean if there is no smoke, but the engine seems to running fine?

[Dave Robelen]

Hi a6m2,
A good test of your mixture is to slowly pinch the fuel line while running at full throttle. If the mill speeds up, you are in good shape. If it begins to die, then you need to richen up the mixture. The other check is to point the model way nose up at full throttle and listen for any sagging.
The absence of smoke may simply be the lubricant package in your fuel. My OS .25 runs strong on the rich side with no visible vapor.
Regards, Dave