® CBX cam and carb interchangability

Each US model year of the CBX1000 has cams and carbs that differ. The 1979 model's intake cams produce the most valve lift and its carbs technology is derived from Honda's carburetors of the 1960s that used an extra, "primary main" circuit. The 1980 through 1982 cams very slightly year to year, but all of the 80-82 intake cams lift the valves less than the 79, and the 80-82 carbs all have one less circuit. There is no correlation between these two specifications.

The 79 cams and carbs are not necessarily the best. Practically speaking, there is little discernable difference in performance, and any year cam and any year carb can be used on any year bike, with no negative outcome. The only real consideration is the effect on collectible bike value when it the time comes to sell. I am fairly certain that the higher-lift 79 intake cams were a liability for Honda (snapped camshafts and excessive cam chain wear) and that is why they reduced valve lift on the later models.

There are maintenance issues attendant with swapping cams around however. The cams' base circles are not the same so a swapped cam will require the adjustment of all the valve clearances, and the carburetor that is the most tunable when doing engine modifications-- including individual K&N air filters-- is the 79 carb with its extra circuit, so that is the carb to have if you have a choice and are planning engine modifications.

A couple minor related things. Due to the more horizontal angle of the 1981-1982 intake manifolds, the carburetor vacuum tops are more easily removed in-situ on these bikes than they are on the 1979-1980 machines. There are two versions of the automatic (vacuum) fuel valve found on 1980-1982 CBX carburetors. The round-bodied valve on 80 and 81 bikes is not rebuildable. The square-bodied valve on the 82 model is rebuildable. The square-bodied valve can be retrofitted to 80-81 bikes as long as its unique mounting bracket is also used. There was also a third version of the auto valve that was sold by Honda as add-on for 79 models that did not come with a valve. This round-bodied valve is unique, having only one fuel inlet to match the 79 carbs.

Don't be afraid to mix and match these parts. All of them, with special considerations, work interchangably.

Last updated December 2021
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