We've been through the carburetor 3 times, the last time by a qualified mechanic. Inspected and cleaned everything, set all jets and adjustments to spec. The end result every time is the bike won't run without the choke unless the idle is cranked way up - which then results in backfiring, hesitation, etc. We've even tried moving the clip to position 5 and turning out the pilot screw, neither of which seemed to help. Engine is good, no cracks in the intake boot, new filter, no exhaust leaks, can't find anything dirty or clogged within the carb or vaccuum leaks anywhere. Anybody have any other ideas or experience a similar situation? Do we need to make more drastic adjustments or start changing jet sizes? It has been about 40 degrees here during the day and I know these carbs can be sensitive, but trying to get some input before buying new parts to throw at the problem.