It is interesting to note that moving into the mid to late 1970s Honda exhibited an apparent austerity program in regard to its powersports carburetors. You can see it in almost every Honda streebike of that era. One of the things they did is they went from having one synchronizing screw on each carburetor to suddenly having one fewer. That is, four-cylinder carbs suddenly got just three screws and two-cylinder carbs, one. Though Honda would eventually characterize three-screw type four-cylinder carburetors as having a “master”—i.e. unadjustable—carburetor, veteran Honda mechanics immediately recognized this as false. And it’s a very misleading description. I submit to you that on Honda’s constant velocity carbs at least, there is no such thing as a master carburetor.

Let’s look at some history. The first Honda carburetor assembly to get this one-less-screw treatment was the 1975 GL1000 carburetor set. Since this carburetor emerged some three years before motorcycles became subject to emissions regulations, and since Honda’s official GL1000 manual says nothing about a “master carburetor”, this carburetor assembly, the first to have the missing sync screw, is itself evidence that something else (other than emissions or a “master carb” ethos) was at play. Note that the GL1000 carburetor assembly also has no overflow telltale system, and just one air cutoff valve for all four carburetors. There was definitely some cost-cutting going on here.

With the GL1000 carb set, instead of talking about a master carburetor, Honda communicates in the official manual that the screw between the two leftside carbs synchronizes those two carbs, the right side screw synchronizes the right two carbs, and the rear left screw (at the end of the linkage that connects the two banks) synchronizes the two banks to each other. And guess what? Kawasaki described the exact same process for their inaugural 1981 KZ1100 CV carbs, which of course are arranged in a straight line instead of the GL1000 carbs’ square shape. Kawasaki instructed that the two carbs on the left were synced to each other, then the two on the right, then the two banks to each other. Structurally and functionally, the KZ1100 carb assembly is no different from the GL1000 set. It is simply the GL1000 carb unwound from its square into a straight line. Both are synchronized in the same way. Most importantly, Kawasaki does not mention a master carb, and even though the KZ1100 was subject to motorcycle emissions standards, nothing was communicated about why the carbs had only three synchronizing screws. Emissions is not mentioned.

What we are talking about is throttle synchronization. It really isn’t normal to think of any of Honda’s multicylinder carburetor assembiles as having a master carb while you are synchronizing them. If you’re used to thinking that way, fine. Good for you. Do what works. But if you aren’t married to that idea, and want to know the reality, instead of having a master carburetor, the VB carb assembly simply has one less synchronizing screw than carburetor, just like the GL1000 and the KZ1100 carbs. And despite “master carb” verbiage associated with VB models such as the CBX1000 and first-gen DOHC fours, VB carbs are synchronized in exactly the same way as the GL1000 and KZ1100.

You can chalk all of this discussion up to semantics if you want to, it just isn’t that important when looking at the big picture. But what I’m describing is the way career mechanics have looked at multicylinder Honda carb synchronization since the very beginning, that is, since the advent of the Honda multi-carb rack. The worst two carbs first, then the next worst, and finally, syncing the center of the set. The master carb principle is really where the semantics exist, and it is not how mechanics with more than a little experience learned to synchronize multicylinder Honda carburetors. When I learned synchronization, there were no “master carburetors”, and yet as I have demonstrated, there were already multicylinder carburetor assemblies having one less sync screw than carburetor. So what changed when Honda started using the master carb terminolgy? Nothing changed. Only Honda’s way of explaining why there is one less screw. Veterans like myself see that explanation as wholly unsatisfactory. It misleads newcomers and causes them to focus on something immaterial to the task at hand, resulting in making the job harder than it has to be, and the results often less accomplished.