Motorcycle Repair: cb650, speed jets, exhaust pipes

Question
I have a 1980 cb650.  I have taken the carburetors all apart and cleaned. Replaced air cut off valve and accelerator pump and some rubber O rings. I bench sync the carburetors.  Set the pilot screws at 2 1/2. After i reinstalled everything it fires up with the choke on just fine.  When you turn the choke off it idles ok but not the best. Once you give it gas it dies.  It well rev up with the choke on. It also seems like the two middle exhaust pipes are hotter then the outer ones. I am unsure what to do please help.

Answer
There are a couple of things that could be going on. The accelerator pump may not be set just right.  Make sure the pump linkage is adjusted so the lever just touches the top of the pump rod and starts to move as soon as the throttle is moved. If there's any delay the engine will stumble as you described. Secondly,  I'd recommend you sync the carbs with a set of gages.  The bench sync' process only get them in the ball park.  They are not sync'ed.  The only other thing I can think of is that the low speed jets or the passages in the carbs aren't quite clean.  I'm assuming you set the float level correctly but this could also make the engine run lean.


Regards
Rich