Quote:
Originally Posted by choneofakind
Please explain this statement, if you will.
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The restricted size of the intake on the airbox compared to the size of airbox creates a certain amount of vacuum inside. Airboxes are designed so that there is enough vacuum to feed the engine the correct amount of air in relation to the stock jet sizes inside the carbs. Pod filters change this. No airbox, different amount of vacuum, different amount of air, different jets and mixture settings required to get running properly again.
No airbox = improper amount of air = harder to tune. Impossible to tune if your bike has constant velocity carbs as my FZR250R does.
You can also mess with the airbox boots. A longer inlet tract (longer airbox boot) will move the peak power and torque to lower in the rev range. The reverse is also true.
http://www.f1technical.net/forum/vie...hp?f=4&t=12772
Linkin's FZR250R 3LN3
The main point here is that to tune a bike, you have to change one thing at a time, test ride, and then adjust mixtures/jets accordingly.
So, for example. You have a jet kit and pod filters ready to install. If you install the jet get and the pod filters at the same time, you're in the dark as to how to tune the bike.
Let's say you have a stock Ninja 250R and you replace the airbox with pod filters. After you do so, the RPM is hanging and will not return to idle. In this situation, the pod filters are allowing more air in, leaning out the mixture. Therefore, you need to adjust the idle circuit to compensate. You'll know you have the correct settings when the bike idles as it did with the airbox. Which means, no bogging down when you twist the throttle, no bogging or stalling below idle speed when you release the throttle, and also no hanging when you release the throttle.
That's just for the idle circuit.
Moving on to the main jets, after replacing the airbox with pod filters, you'll ideally need a dyno and AFR readings to tune any rich or lean spots.