i would say the pilot jet in the carb has been blocked or severley narrowed by some debris,take the carb off and float bowl off and take the jet out and make sure its clear and the hole is not narrowed i use a set of jet drills i have to check them by simply running the relenat drill but through,for instance a 45 pilot jet needs a 0.45 mm drill bit ! they go right down to 0.2 of a mm bit like a hair that cuts !
adam bike doctor
April 2010