It happens, during taxi I have been trying my best to lean out, today I must not have leaned hard enough because i forgot to enrichen it before taking off. I lined up for takeoff gave full power and the engine seemed to be making full power, I didnt notice any thing unusual. As i was upwind about 1000 agl i looked down and saw the mixture still lean, pushed it full rich and only seemed to notice a slight increase in engine RPM, which tells me it was not leaned out very much but oddly enough as I recall from memory, the mixture was leaned out at least an inch or so, maybe even more. Always learning and something to learn a lesson from, before EVERY takeoff its "lights, camera, action, everything forward". Anyone else ever done this?