Plowboy, If you can see a gray trail coming out of the motor while running then you are not too lean. That is a good sign that you are not running lean. The engine may have been running too rich before you adjusted it, you now have it in the sweet spot which produces good RPM, but is not running lean. If it was too lean, there would not be a noticeable smoke trail coming from the engine. Signs of overheating a engine would be to have Pre-detonation (a tapping or knocking sound) would come from the motor if it were too lean (overheating). Pre-detonation is when the piston is coming up on the compression stroke, the fuel will explode early due to the extra heat created from friction and lack of lubrication on the cylinder wall. The cylinder will expand and seize against the sleeve (Melting the cylinder to the cylinder wall). In pre-detonation the expanding gases will push down on the piston before TDC (top dead center). This is when the engine will start working against it’s self. If the explosion is too soon, the piston has to work harder to reach the top. The sound you hear is a pinging or rattling type noise usually just before the spinner and prop start to fly off. Pre-detonation is very bad...

Hope this helps,