hey guys, i have a keep off plus 4 .21 and seems that air is getting in and i can't tune it! I have noticed that when on throttle the tuning is ok and off throttle the engine gets lean... I try a lot of different settings on the carb , resetting the needles, try again, have my buddies check on it again in order to exclude the possibility I'm doing something wrong.

Front ball bearing is changed recently and i'm pretty sure that it's air insulation problem. Anyone having experience with this ? What i can do and what to check?