You know, that was the first thing I tried. I figured it was either overfilled or running gear oil instead of the 10W-40 specified in the book. I let it drain overnight, then filled the case again. It worked well for a few days, then started pumping out again. Pretty weird, considering how much higher the vent is than the oil level. Even allowing for expansion of the oil, it shouldn't be coming out of the vent! The only thing I can think of at this point is that the chain might be carrying the oil to within striking distance of the vent, or, like I said in the beginning, crankcase gasses could be passing through the seal and foaming the oil. I'd think there would be performance issues there though, and the oil looks bubble-free. Puzzling. Thanx for the comeback though.