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Join Date: Jul 2006
Location: Kennett Square, PA
CA emissions are tougher than the rest of the country, so whatever you do to fix the problem (outside of an exhaust leak), make sure you can un-do in time for the inspection.
The air/fuel adjustment screw on both cylinders is factory set at 1 5/8ths turns out - most folks find that way too lean, and that's what creates the popping on decel. If your bike is new or no one's ever messed around with the setting, the screws will be behind small bits of lead - holler if you can't find 'em, and the Forum folks can walk you through getting the lead out (ha ha). The screws can be turned back to the factory setting before you go for inspection.
If that doesn't work, then try "coastering" or "marbling", as folks are suggesting. The easiest way to do this is to stick a marble in the hoses leading to the reed valves on each side of the engine block. This cuts off the air flow that Kaw introduces into the engine to burn unburned fuel in the exhaust (thus creating the popping) - it's to reduce emissions. Again, the marbles can be removed before your emissions inspection, if that turns out to help the problem.
The backfiring - kaboom! versus "pop pop pop" - is probably due to a leak in the exhaust, so check that first and tighten up all fasteners (your torques can be found in the Clymer's manual and I think there's a list in the Verses). Any idea which side the backfiring is coming from?