I'm trying to start a new unknown engine that's on a 1/3 scale citabria. It's never been started and I don't know how to set the screws for starting. The engine looks like a zenoah but the label says "U.S.E. Engines-Syracuse N.Y." I tried to Google them and yellow pages but no luck. The carb looks exactly like a zenoah. There's a high speed and a low speed screw. How should the throttle be set? !/8? 1/2? Full? The carb doesn't seem to want to take gas. I removed the fuel line from the carb and applied air pressure to the overflow line and the gas flowed freely. But when hooked up to the carb the fuel doesn't move through the line when air pressure is applied to the overflow. Any info is greatly appreciated.- Arnold