I am adjusting my weber 40 IDF floats. The weber tech manual says to have the float set to 10mm in the up position. The question is it 10 mm with the damper ball pushed into the needle valve?

My instructions said, 10mm when the lever on the float just touches the ball, but doesn't push it in.

Tommy

Just touching, not pushing. And they say 12mm works better.

Thats what I thought. If I want to lean the mixture using the floats, do increase the measurement from 10mm to say 12mm?

The float is just to keep enough fuel in the bowl to feed the engine without overflowing. Think of it just like your toilet. Just enough water in the tank to flush it. Not too much, not too little. Use the jets to adjust mixture.

The float sets the fuel level in the bowl. This doesn't affect the mixture. I did learn that if not adjusted properly the fuel level can get too high and raw fuel will spill into the carb throats, ruining the engine performance!