It seems to me if the front bearing is leaking fuel that may have been caused by a rich engine setting, that bearing should be replaced. Two stroke engines run off of crankcase engine pressure. In order to have a good smooth running engine, that crankcase pressure must be continuous and even. Any air or fuel leaks will affect the engine negatively. This is why a new engine runs better than an old one, crankcase pressure is maintained throughout the two stroke process, both positive and negative pressure  this is also why a good piston/liner seal is imperative to smooth and strong running. If the front bearing seal has been compromised it is time to replace it. Leaning the engine out to reduce fuel leakage is amateur. If leaning out the mixture reduces the amount of fuel coming out of the front bearing it will then push air out thru the front bearing in place of the fuel which is not good either. Replace the bearing correctly and you will take care of the problem. Another thought, if your engine is running on such a rich mixture that its pushing it out of the front bearing, its probably time to replace the piston and liner as well. Good luck and if you have any questions about changing the bearing please dont hesitate