hex0rz
+1y
Before I go any further, have you tried checking your float in the carb? I would highly recommend checking to see that it is adjusted right. This is starting to sound like a float problem to me.. I will keep reasearching this dilemma of yours..
EDIT: Meanwhile, check out this page to make sure you do not have these problems. If you feel you have more than one problem, highlight the causes in each section to check off what it most likely could be.