Hi,
I always balance the carbs on mine by ear.
Stage 1:-
Fire up the engine and leave it idling, then listen at the silencer outlets. You will be able to hear if one cylinder is "lazy" - in that case, turn out the throttle stop of the lazy cylinder slightly. Keep tweaking until both exhausts sound the same, and if the idle speed is then too high or too low, turn both throttle stop screws in or out by the same amount to set a nice idle.
Stage 2:-
If you have an assistant stop the engine and set the throttle so that one slide is just disappearing from view at the top of the carb bore. get you slave/assistant to hold the throttle there while you go round at check the position of the slide on the other carb. Adjust the carb top cable adjusters as necessary until both slides disappear from view at the same time. This gives a rough balance close enough for normal riding. (Without an assistant stage 2 is nigh on impossible - in that case move on to stage 3!)
Stage 3:-
At the handlebar end of the throttle cable, unlock the adjuster and tighten it until the engine speed rioses to a fast idle (about 2500 rpm). Then listen at the silencer outlets again, but this time tweak the cable adjusters on the appropriate carb top until both exhausts sound the same.
