Grand Prix 500
Main Motorcycle: 1973 TR7
Join Date: Jul 2012
Location: Hickory Creek, TX
Sounds like carbs aren't the issue, if you can swap from L-R and the problem remains. Lends itself to ignition, or lack thereof. Boyer's are wasted spark, so as other have said, if it is firing you should be getting one heck of a backfire at some point, bare minimum.
If the plug is firing outside the cylinder when grounded, and the plugs are new, try this experiment:
Find a ring terminal that will fit around the plug body. Put a short lead on it, and run the plug through it into the head. Run the lead to a head bolt, or similar ground location and see if you get fire. This will elminate a problem with the ground side of the equation for the plug.
If you still are dumping gas, it almost has to be a the carb. I would "bench test" the carb just for kicks, and as you said they are mikunis, make sure the enrichment circuit is closing properly. If it is flooding through the enrichment circuit, you may not get any fuel flowing out the overflow tubes.
A GOOD friend will bail you out of jail, a TRUE friend is sitting on the bench next to you saying "Damn, that was fun!".