If the engine is running smoothly at higher RPM and isn't making any weird noises then it's possible that your engine won't idle for the same reason that the bearing is leaking. Your LSN setting may be way too rich. Try leaning the LSN significantly (may need to reduce the carb's idle gap too) to see if you can get the idle better. If the idle improves with this then I bet the leaking goes away. Front bearing seals aren't air or water (oil) tight and if there's a bunch of extra oil in the crank case then it will come out the front bearing, even if it's new.