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Keihin pilot jet comparisom

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Came across this picture on borynack's website and now it's really peaked my interest. The picture shows a "S" pilot jet and non "S" pilot jet. Both are factory Kiehin 68 pilot jets. These jets are for his 650R. There is quite a difference in the passages between the 2 versions. Anyone here know if it is the same for the pilot jets in our L carbs? (specifically the passage sizes between the short and non short versions of the same size jets)

Just kinda curious as I think it could make a noticable change in the way the motor runs at idle and low throttle.

kehin68svsnonspilotjetsfromborynack.jpg

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Those are emulsion holes that mix air with the fuel before it gets sent into the engine. AFAIK, the smaller holes make for a slightly richer mixture with the same jet size.

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well this is what i found about the S jet.......

#5 Q: What's so special about the "S" in a 68s pilot jet? The 68s has smaller holes than a standard pilot. It will change the flow characteristics and atomization of the fuel. You can run a regular jet in there if you want, but then you won't be on the same playing field as the rest of us, meaning that we can't help you! The PN for the 68S is 99105-MBN-0680. If you need larger, just substitute the size you need where the "68" is.

So its like having a smaller jet, why they have that i dont understand, unless its kinda an inbetween size from the 68 to next down. Never heard of anyone using a S in the L. besides we dont really use a pilot that huge.

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The "S" jets run a little richer than the non S jet. The effect is small and I can't say that I really noticed a difference in my XR600 between the two.

If I remember correctly the S jets might only be available from Honda.

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on the L the 26 series(N424-26-xxx) is the one of the correct length 23.5mm

the one sometimes used successfully is the 21 series(N424-21-xxx) it's a bit longer at 28mm and sometimes requires the slosh baffle to be trimmed

i don't have both to check the emulsion holes size but my SWAG is they are the same size...

scroll down to "Pilot Jets" for the drawing.

http://www.motorcyclecarbs.com/Keihi...har_W56C69.cfm

:)

P.S. i just check the L's 26 against the R's "s" style and the L's 26's have the *EDIT* larger holes...still unsure about the 21 series.

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well this is what i found about the S jet.......

So its like having a smaller jet, why they have that i dont understand, unless its kinda an inbetween size from the 68 to next down. Never heard of anyone using a S in the L. besides we dont really use a pilot that huge.

I think the 68S is not a smaller jet. Those are just the SIDE hole you're talking about. I think the inner diameter of the 68 and 68S are the same. I think that you think that the fuel comes out of these side holes, well maybe but there is also a hole on the end of it too.

:D Could be wrong and it wouldn't be the first time.:)

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I think the 68S is not a smaller jet. Those are just the SIDE hole you're talking about. I think the inner diameter of the 68 and 68S are the same. I think that you think that the fuel comes out of these side holes, well maybe but there is also a hole on the end of it too.

:D Could be wrong and it wouldn't be the first time.:)

That's correct. The 68 means teh hole that the fuel passes through is .68mm in diameter. The side holes are the serve to mix the fuel with air.

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