My OS .91 FX has some kinda leak somewhere, won't richen up. No air bubbles from the needle to carb so I sealed the carb and set screws with some Hi-Temp silicone. Haven't tried it yet (silicone not dry) but will let you know. The jury is still out on this motor, not real happy so far. I'm running 5% and a 3 blade 12/7. Seems to keep the High rpm just right.