I wouldn't say that's a problem. When you put your finger over the carb and rotate the crank, the cylinder will and is supposed to draw air/fuel from the carb. With your finger over the carb, you seal the system and it draws a much higher vacuum. Since it can't draw air (finger blocks this) it pulls a ton of fuel through the only other escape, the fuel lines. As you rotate the crank further, the piston drops below the exhaust port and the vacuum you created is lost though the exhaust. No vacuum, no fuel draw, and you should be able to feel this with your finger too.

BTW: That's how we prime the engine with fuel at the start of a flying day.


All that said, it could still be a tank problem. I think I'd check the clunk first to see if it's installed properly. I nosed in once, and the clunk "flipped forward" in the tank and hung there. Cause all knds of weird problems.

I'd pull the pressure line from your muffler and blow through it, see if the system builds pressure and fuel moves to the carb.

I've got a .61NT and I'm trying to think what else..... Heck I've flown it without the pressure line before. It run a little lean, but really I couldn't tell that much. I guess it blew off, not sure how that happened.