There was a small pipe that you fit to the carb to bring the breather or whatever it was out into the flow of air (caused hesitation in unmodified carbs)
From zuhwarrie site
Engine hesitation:
The stock carburetor has a flat-spot around 3000rpm. This is caused by the drop in vacuum in the manifold through the vent hole in the secondary throttle plate, causing the secondary to not open properly. The simple addition of an inexpensive carburetor vent tube will cure this problem. This OEM part is available from several of the Suzuki aftermarket companies
http://www.izook.com/shoptips/vent_tube_fix.htm is the site for the kit and a write up also.
Hope it helps.