In another article I mentioned that jet kits are "fixes in a box". That is, more or less silver bullets designed to, in one stroke, solve the results of poor maintenance. Factory Pro, Dynojet, and their ilk represent this ethos consumately. The plain fact is, a vintage Honda that works better with a Dynojet jet kit is one that has maintenance shortcomings that should be attended to instead. In the model Hondas I am most familiar with, the CBX1000 and first-gen DOHC fours, the Dynojet kit absolutely drowns the carburetor in fuel. Any perception that this actually makes the engine work better is a serious red flag. You will recall from previous articles that as maintenance is neglected, the carbs lean out. The reason has to do with combustion efficiency, but it happens. If maintenance were kept up, the carburetors would have less demand put on them, and they would automatically act better, richer, because combustion is optimum when the engine is in good condition and tune.

You should not interpet what I say about the Dynojet jet kit as some kind of angst about the Dynojet company. The former vice president of the company and I are friends and longtime colleagues. I have met Mark Dobeck the founder, I very much respect what he did and what the company does today, I have experience collaborating with Dynojet's tech staff, and I have observed that Dynojet kits seem to have valid application apart from the two Honda models I just mentioned. I have no bone to pick with the company. The question is, why are these two model lines negatively affected? I don't really know but I have thought about this a lot and my theory is that when they developed the kits for these bikes they had in their possession machines with significant maintenance shortcomings. In the CBX and DOHC, this almost surely means tight valves, the number one malady of these engines. The bikes used were non-representative of their kind, making the jet kit development skewed. That's what I think happened. Maybe not, but the fact that the kits don't work is not in question.

On a related note, forums insist that vintage Honda VB series carburetor slides must be replaced in a carburetor that is having a Dynojet kit removed, presumably because of the enlarged slide lift hole. First, Dynojet kit reversal is in fact "a thing". It happens among 70s-80s Honda carburetor rebuilders a lot. Second however, is no knowlegeable person replaces the slides. There just is no need to.

What Dynojet was trying to do with the slide hole enlargement was make the vacuum slide rise differently. A Honda CV carburetor's slide does not rise in direct or linear proportion to throttle opening. It lags a little. This is a good thing and is why CV carbs work as well as they do, particularly in the area of throttle response. Enlarging the hole causes the slide to delay less, i.e., lift faster and more linearly, in this way mimicking a variable venturi (mechanical slide) type carburetor. The thing is, this effect is noticeable to only a very small group of people. The effect is slight and works only when wide open throttle is part of the throttle opening change. Racing, in other words. It just isn't noticed on the street. For this reason, the enlarged hole will be invisible to most riders. It can be left as-is. I have done so on countless CBXs and DOHCs.