I also prefer the chemtool B12, but either way, some cleaner in the tank can't hurt and may do the trick. I was having a little problem with my choke/enricher circuit earlier this season. After putting some (cleaner) in the tank, and repeatedly running it with choke on for a little longer than usual, it helped.
Try draining the float bowls first, to see if there are any large particles in there. You can easily do that with the carbs still on the bike. If you find any crap in the drainage (there shouldn't be) there could be a couple of reasons for that we can discuss later. After draining, run some cleaner of your choice from the above options thru the system to see if it helps.