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just wondering. lots of people say you should always put a jet kit on a bike when you change the pipe. what i want to know is how you know that the new fuel mixture will work with the new pipe. are there different jet kits for different pipes? can i add a slip on without jetting or will that put me in danger of over leaning? my bike is a '00 9R.
 

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You don't necessarily have to re-jet with a slip-on. There are many factors at play: 49 state vs. CA bike, altitude, make of pipe, etc.

The most accurate way to test is before & after dyno runs. As this is not usually very practical, try finding someone with the same setup who has already done the dirty work and can simply recommend whether or not to jet and what size.

Different pipes may require different size jets, but not much. You will not hurt your bike by installing a pipe and not re-jetting. Put the pipe on. If the bike does not run as smoothly, seems to have power loss, or is returning much worse than normal gas mileage, you probably need to re-jet. Bear in mind that the slip-on may move your bike's power and an increase in one area usually comes with a decrease in another.
 

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On your 2000 ZX9R you should not to rejet for just a slip-on pipe. If you do the full exhaust you don't necessarily need to rejet either, although in most cases rejetting will yield you more power and smoothness throughout the RPM range over stock, as stock jetting in calibrated lean for emissions, etc... Most manufacturers will tell you when they recommend a rejetting.

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Just shim the needles! I havent done it on my 9 YET but its easy and almost always produces good results, not to mention its extemely cheap!

 

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Shimming the needles only works in the mid range. To get full advantage you need to change the main jets. Which works from 1/2 to full throttle.
 
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