Hey Petey
I expect your air cooled '06 is just jetted very lean and needs more warm up time than you expect. An adjustment to the air screws would likely help. This would mean removing the carbs and drilling out the air screw plugs, then start by setting them at 2-3/4 turns out.
But if you've got the carbs out that far, you might want to consider a jet kit, or at least a shim under the needles and possibly one size larger main jet. Fuel mileage will go down a little, but you'll pick up more HP and better driveability.