I didn't get to fly this past weekend because we got dumped on by mother nature. Instead, I took an old glow plug, drilled it out, and silver soldered a Dubro nipple onto it. I hooked an air hose up to it, plugged the carb intake and nipple, and the muffler nipple and exhaust, and applied 5-10 lbs of pressure to it. I then submerged the engine in water and watched for bubbles. I was really amazed at how tight the engine was, without adding rtv anywhere. as I rotated the prop, the air would pass from the cylinder to the crankcase. When this would happen, air would come out the front bearing, but nowhere else. As I rotated the carb barrel from fully open to fully closed, I got a little bit of a leak around the end of the barrel when fully closed. Hardly enough of a leak to mention. After this test, I pulled the engine apart, including pulling the front bearing, and oiled everything up real well. Once I saw the machined channel for the oil return at the front bearing, the air loss there made perfect sense. I am no longer concerned about that at all. I am all the more convinced that the problem with this engine was fixed when I changed the spray bar. The poor transition in a hover, in the frozen climate, I am convinced is related to the engine being so new, and the fuel thickening from the cold. A higher nitro content would likely help in this area.

I honestly didn't expect to find this engine so air tight. I didn't even see the leak people talk about around the carb jamb nut. You may recall though, that I had changed that o-ring when I damaged it taking it out of the housing throat. The one supplied by GMS seemed rather hard and stiff.

Andy