Ninja 250 Carburetor Needle Information: Difference between revisions
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The needle in a carburetor is the main method of adjusting the mixture at partial throttle openings. It blocks some of the passageway to the main jet (the main jet size determines the carb's overall mixture), reducing the amount of fuel allowed to flow at part throttle. This keeps the mixture consistent through a range of throttle openings: as the throttle opens, raising the slide, the needle also raises (it's attached to the slide). The needle has a tapered profile, so that as it pulls out of the main jet port, it blocks less and less of the port, allowing more fuel to flow, ideally matching the amount of air flowing through the carburetor. By the time the carburetor is at full/wide-open throttle, the needle is completely clear of the main jet port, allowing it to flow without restriction. | The needle in a carburetor is the main method of adjusting the mixture at partial throttle openings. It blocks some of the passageway to the main jet (the main jet size determines the carb's overall mixture), reducing the amount of fuel allowed to flow at part throttle. This keeps the mixture consistent through a range of throttle openings: as the throttle opens, raising the slide, the needle also raises (it's attached to the slide). The needle has a tapered profile, so that as it pulls out of the main jet port, it blocks less and less of the port, allowing more fuel to flow, ideally matching the amount of air flowing through the carburetor. By the time the carburetor is at full/wide-open throttle, the needle is completely clear of the main jet port, allowing it to flow without restriction. | ||
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partial throttle. | partial throttle. | ||
You can also "adjust" the needle by substituting | You can also "adjust" the needle by substituting different-profile needles for the stock units. There are practically two ways to | ||
do this: you can purchase a jet kit, or you can try needles from other carburetors. Enterprising riders with machining skills may also manufacture their own needles on a lathe, but this is beyond the scope of this article. | do this: you can purchase a jet kit, or you can try needles from other carburetors. Enterprising riders with machining skills may also manufacture their own needles on a lathe, but this is beyond the scope of this article. | ||
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Reprofiling a stock needle is a job for a machinist, and is beyond the | Reprofiling a stock needle is a job for a machinist, and is beyond the | ||
capabilities of most Ninja 250 owners. | capabilities of most Ninja 250 owners. | ||
The Ninja 250's stock carburetor is a Keihin CVK30. | |||
The stock needle is marked N16I at the top, and is Kawasaki part number 16009-1461. It's made of brass. | The stock needle is marked N16I at the top, and is Kawasaki part number 16009-1461. It's made of brass. | ||
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[[File:jetneedle-horiz.jpg|right]] | [[File:jetneedle-horiz.jpg|right]] | ||
BrianM submitted this information about an aftermarket jet needle. He was unsure which needle it was, but as the measurements don't match those of the Factory Pro needle above, it's | BrianM submitted this information about an aftermarket jet needle. He was unsure which needle it was, but as the measurements don't match those of the Factory Pro needle above, it's likely that this is the DynoJet needle. | ||
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