Motorcycle Repair: 1980 Yamaha Midnight Special XS 1100, xs 1100, chemtool

Question
We have a 1980 Yamaha Midnight Special XS 1100, it does not run smooth. It is bogging out and back firing.  The two highly recommended shops in the area have said the the cars "look fine" and another rebuilt them for us - we have run B-12 Chemtool as well. Sometimes it will run OK but not for a whole ride... I am frustrated and don't know what else it could be.  Any help would be appreciated.  Thanks from T-Town

Answer
I can understand your frustration, but I'll need some more info before we can start to track down the problem. From what you've told me so far it appears that you believe the problem is with the carbs. However, I need to know for sure if this is a fuel system or an ignition/electrical problem, so I have a few questions for you...

Does the bike run poorly right from a cold start or does it work good for awhile and then start to lose power as the motor gets warmed up? Did the bike always have this problem or is it a recent occurrence? Does it happen at low speed, high speed or any speed? Has there been any major repairs or servicing done to the motor recently? When the carbs were rebuilt, did the shop synchronise them afterwards? When was the last time the gas tank was flushed and cleaned out? Are there any electrical problems not related to the motor that you are aware of?