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While installing my jet kit last night I was very surprised to notice that my carbs had different size main jets in them. The "outside" two carbs had 140's in them while the inner two had 142's! I called my local Honda dealer about this today and they told me that this was standard practice on the F4's, but they didn't think it was on my bike (cbr1100xx) and the Factory kit I used didn't make any mention of this as well, sending 3 different main jets in sets of 4. Anyone else heard of this before? Thanks for any info you could provide me with.

Kyle

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That's not too unusual. My Super Hawk has different main jets between the two cylinders. Your outer cylinders run cooler than the inner.

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--2000 VTR1000F Super Hawk
 

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It's true. R6's are set up that way, too (except the richer ones are on the outside). If your stock jets came out that way, I'm sure it's correct.

Often, aftermarket jet kits won't address this setup, but they seem to work anyway. If you use a Dynojet kit in an R6, for example, they use all the same mains, but if you use the Yamaha factory race kit, they retain the staggered sizing...

Go figure!

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I'm not joking. And don't call me Shirley.
 

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One more point, in case there's some confusion...

If your outer main jets are richer than the inners, it's because, as El Diablo said, the outer cylinders run cooler.

However, as in your bike's case, the reason some bikes have richer inner mains is probably due to airbox design. Your inner cylinders are probably sucking in more air than the outers, therefore requiring more fuel as well.

So basically you can have any combination, as the factory deems necessary...

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I'm not joking. And don't call me Shirley.
 
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