I have a pw 50 that dies when warm?? It's a fresh rebuild with all new parts, piston, rings, jug, stator, coil, carb, fuel pet cock, cdi, rectifier. It starts and runs great when cold and after 15 minutes or so dies! The sound of the engine even changes. Sounds like it is starting to load up/seize. Oil injector is working great but for trouble shooting purposes I am running pre-mix. Any and all help is appreciated.