Taildragger, I love the G-90's, I have 2 of them and only problem I have ever had was it didn't want to come down to idle when new. It would do like a fast idle for 30 sec. or so then go to the nrmal idle speed. I changed to a perry carb but that didn't help. All it needed was broke in. Other then that mine start up fast and run great! I always take a new engine's rear plate off and wash it out then I go over every screw to make sure everything is tight. And if i have any trouble starting then I adjust both needle valves. I hear alot of problems with engines but maybe im lucky but i have O.S. 2 and 4 strokes, Thunder Tiger 2 strokes, Super Tiger 2 strokes and Magnum 4 strokes and I like them all. Some need to be adjusted a little more then the factory settings but they all run good. Check for air leaks and make sure it isnt running too rich if it stops when the heat is removed. Hope you get it working because it is a good engine.