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175 S keihin main jet

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Well fondling thru my jet stash as i need to buy some tonight i see i have a Keihin 175 "S" main jet, now i know there is S for pilots but a main? its one hole only so what the heck is the difference? something with the taper inside or who knows LOL

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I was always under the impression that "s" means it was the (s)tock jet in what ever bike it came from.

But I have been wrong before.

Keihin does not even list an "s" jet.....

http://www.keihin-us.com/list.htm

the only S ive seen is on the pilot jets, ie 68s and the s for small orifice so its kinda wierd to see one on a Main jet

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There are "S" main jets and "RD" main jets and it has to do with how far the orface in the venturi of the jet. The "RD" is way down low by the fuel and the "S" is higher up. I think it also has to do with the over all length also but, it has been a few years sense I read all this. I have an RD and it idin't run the same in a XR400R as a stock type jet. I may have a "S" main in my stuff also but, I never use it......It should have something to do with the mixing of the air with the fuel.

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the overall length is exactly same as all my other main jets, ill look inside it, see if i can see anydifference in the inside, was just wierd to see it as i threw a bunch out on desk this morning seeing what i had and what i need to buy.

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