Pod filters and rejetting?
The short answer is " probably". But, for those that are curious...
Honda selected the jet and air orifice sizes to operate with the engine as it was delivered from the factory. Many things contribute to the way the engine breathes: cam timing and lift, valve size, piston bore/stroke, exhaust restriction, and, of course, intake flow characteristics, etc. The characteristics of each of these items have a profile or rating at each point in the expected RPM band of the engine. For example the exhaust and intake profile will vary, not necessarily linearly, and not on any smooth curve. There can be dips, valleys, or spikes in their flow characteristics. While each individual device is engineered to provide the best characteristics or the best cost benefit ratio, these components all interact when assembled into a complete machine. Then the carb metering devices are adjusted (or selected) and tuned to provide the correct fuel/air mixtures for power and economy for each RPM setting.
The CB550s have three fuel metering paths in the carbs. There are also numerous air metering paths to emulsify the fuel with air before it dumps into the carb bore on it's way to the engine. These air paths effect the mixture ratios, also.
While all the fuel metering jets have a function at all RPMs, the main jet is selected to provide for the fuel demands at wide open throttle (WOT). The slide needle taper profile (also depth setting) and slide jet provide for the fuel demands over the midrange RPMs. And, the pilot or idle jets provide for the fuel demands for low RPM operation.
Few people have much respect for the Honda engineering prowess. Or so it seems, as people routinely change the bike from it’s stock configuration. The reasons why are as varied and numerous as the people who perform these changes. But, it seems the people that understand the total ramifications of the changes they make are very few in number. And, even fewer of these go on to make the proper adjustments to the machine in total to achieve equal or better overall performance.
Usually the first things changed are the intake and exhaust. Whether for looks or cost or just something easy to make the bike look different doesn’t really matter. But, unless the replacement components have the exact same flow characteristics as stock over the entire operational RPM band, carburetor adjustment and tuning are very likely to be needed.
Honda knew this and made the necessary adjustments.
Between the 1972 CB500 and 1978 CB550, there were 4 carb setups from the factory. These differences were due to changes in displacement, exhaust type, and completely different carburetors introduced in 77. All these bikes used basicly the same air plenum and air filter before the carbs. If you look inside that plenum you’ll find a rubber funnel for each carb intake that acts as a velocity stack. This helps keep the airflow into the carb straight, minimizing turbulence that can cause a notch in the induction flow charateristics, across the RPM band. The engineers at Honda thought they were important enough to include on the production bike. Do your pod filters have this velocity stack built into them?
Can you make changes in your bike and have the engine still run?
Of course!
Will it run as good as one in the stock configuration? Possibly.
But, unless you are willing to test for improvement and make other changes to compensate for what you’ve changed, you’ve got to ask yourself one question. “Do I feel lucky?”
Well, do you?
