This video shows the two-step process on how to perform the proper carburetor synchronization on the Honda CB450 / CL450 / CB500T family of motorcycles. The process is shown on a CB350 set of carbs, however, the same exact process is used on the CB450 carburetors as well.
Step one - setting the idle speed synchronization, aka "bench sync." Step two - adjusting the progressive synchronization, which means having the carburetors open and close at the same rate when the throttle is twisted.
New throttle cables and a throttle sleeve ensure smooth and proper synchronization.
Parts you might need:
CL450 / CB450 / CB500T Throttle Cable: http://www.common-motor.com/honda-450-throttle-cable
Nylon Throttle Sleeve: http://www.common-motor.com/honda-throttle-sleeve