I have been attempting to balance the carbs of my ZXR250C using a Carbtune Pro, and I have not had any success. The problem is that adjusting the screws has no predictable effect upon the vacuum levels, and even if, by chance, I manage to get all four aligned, it is impossible to keep them aligned. If I leave the bike idling, touch the throttle, or stop the engine and restart it, the levels will move substantially out of alignment again. The procedure I followed was to: Splice the dampers into the hoses; Attach the hoses to the carbs; Start the bike and let it warm-up for five minutes; Adjust the screws for cylinders 1/2 and 3/4, then the middle screw; and Open the throttle slightly to see whether adjustments were 'stable'. It doesn't seem to be too complex a thing to do - am I completely missing something :?