I have a Super Tiger .61 that I have had for several years. I just put it on a new plane. After tuning the engine on the ground it seemed to run great. The problem comes when I pick the airplane up and hold it in a vertical position (or upside down); it dies. If I quickly lower the airplane to a level position it will regain itself and continue to run just fine. I have tuned and retuned everything I can think of to no avail.

Any ideas? Do you all think this is an engine problem, or a fuel problem? Please help. Thank you all in advance.

Check to see if the clunk comes close to or hits the back of the tank when held vertically, it could be sucking up against the tank, cutting off fuel supply.

I had one do that, the fuel line to the clunk was off inside the tank. Took me a while to figure it out.

As a matter of fact, the clunk does hit the back of the tank. I didn't even think of that. I guess I will take it out and shorten the fuel hose to the clunk. Hopefully this will solve the problem. I will let you all know.

Thanks so much.