[yorkie_chris]

There's a balancing screw on the linkage, sticking up at rear left of carbs. These can get a bit sticky but are easy to free off (steel in steel, no dramas)
Usual ones to seize up are the mixture screws which are underneath the carbs, these are brass into pot metal/cast zinc and can be a nightmare.

By the way if you do take bike to Stewarts he is one of the most knowledgeable guys I know, definitely recommended.