Honda CB360 Carburetor Synchronization

Posted by on 1/31/2014

Carburetor Synchronization is one of the most important engine tuning steps on a motorcycle (or any engine) with multiple carbs, and the CL / CJ / CB360 are no exceptions. In order for the engine on your bike to make it maximum horsepower, run smooth and idle well, synchronization is a must. Many novice mechanics are very intimidated by the procedure, but with the right tools it relatively easy. Symptoms that your bike needs to have the carbs synced include: High idle speed, inconsistent idle, shaking while accelerating and mediocre throttle response, lack of top end power output from the engine. Chances are your CL / CJ / CB360 has not had the carburetors synchronized since it left the factory so it is time you do it.

So what is carburetor synchronization? It is the adjustment of multiple carburetors on an engine to flow the same amount of air to their respective cylinders. There is a lot of Internet talk about mechanical or "bench synchronization" of carbs; this is typically performed with a small diameter of wire or drill bit positioned under each throttle butterfly while the sync screw is adjusted until equal drag is felt when pulling the bit out from the butterflies. While this will get the carbs close enough for the engine to run, vacuum synchronization will adjust the carburetors properly based on each cylinder's demand.

The CB360 will require a few different tools and adapters to get the adjustment correct and we have made it painless with a carburetor synchronization tool kit.The CL / CJ / CB360 carburetors have a particular size vacuum port and requires a specific vacuum adapters which are included in the kit.

Synchronization should only be performed after the cam chain and valves have been adjusted, ignition timing set and carburetors rebuilt and have either factory air filters or pod filters in place. The carbs must have no air leaks. If you are in question of an air leak then change the diaphragms, intake manifolds and check throttle shaft ends for a missing plug. An air leak will result improper synchronization due to false readings on the vacuum gauge. A box fan will help keep your bike cool while you are performing the synchronization since the engine may be idling for some time.

Fellow CMC member Tom Martin and myself documented the synchronization on his 1975 CB360T in the streets of Brooklyn, NY. We prepared the bike by properly warming up the engine, re-positioned the gas tank, and set idle speed to 1100-1200 RPM. Follow us through the procedure from start to finish.