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naldz006

170s main jet

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hey guys,

just changing the jets on my 650r. Going by the jetting page on the 'pig pen' a 170 main will be about spot on for me. I have a 170s jet that came with my wr. Is this likely to be any better or worse than the normal 170 jet?

cheers.

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hey guys,

just changing the jets on my 650r. Going by the jetting page on the 'pig pen' a 170 main will be about spot on for me. I have a 170s jet that came with my wr. Is this likely to be any better or worse than the normal 170 jet?

cheers.

Hu, something seems a little funky here. So your WR has a keihin PE carb?

I have never heard or seen (i did a brief google search, and keihins website) of a main jet with a "s" designation... you have a hex main jet with an "s" stamped on it? doesn't make much sense.

Are you sure your not confusing the pilot with the main? there is such a thing a s a 70 pilot and a 70S pilot. Go back and double check...pull the main out of the XR and compare it to that 170s main (<--if thats what you reall have)

let us know what you find

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yeah i know it sounds odd. this is a pic of the jet. i'm guessing it will fit, ill put it in when i get a chance.

170sjet.jpg

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yeah i know it sounds odd. this is a pic of the jet. i'm guessing it will fit, ill put it in when i get a chance.

170sjet.jpg

That jet will definately fit your XRR carb. I have never heard of a 170S main jet. There are pilot jets for that carb that have an "S" designation after them, but I've never seen a main like that.

It isn't just the PE that uses that style of main jet. I know for sure that the PJ (2 stroke) and the PWK (2 stroke) also use the same mains. I am sure there are other model that do also. The float assembly from the PJs and PWKs also will fit the PE perfectly. My 650R's PE carb has a PJ float in it right now.

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I've encountered S main jets. They've all been the stock main jets in Yamahas. As far as I can tell, Yamaha specs a main jet designated with S (i.e. "stock" ??) on some (all?) of their bikes. I believe they are identical to normally stamped main jets.

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The 170S will work fine. All Yamaha stock main jets I've seen are stamped with an "S".

Its the same as a "normal" 170.

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yeh i put that jet in and its running better now. dont know what the old jet was.... had no markings on it.....bit dodgey. the bike still crackles a little bit under decelleration but it is better than it was. I might try a 172 main in it when i get a chance. it does 180kph now and still pulling a bit. pretty impressed really. hangs with the wr till 100 then keeps pulling. wish they still sold them over here so i could have got a new one.

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hey guys,

just changing the jets on my 650r. Going by the jetting page on the 'pig pen' a 170 main will be about spot on for me. I have a 170s jet that came with my wr. Is this likely to be any better or worse than the normal 170 jet?

cheers.

An "S" jet is a half step larger than the jet of the same number without the "S". i.e. A 170S jet is a half step between a 170 & a 172.

I have never tried a "S" main jet, but either a 68S pilot, or 70S pilot is a must have in the 650R in my opinion. an S pilot jet will wake the low-mid range up and produce a major power difference.

my 650r has a stock engine, all the HRC un-corking parts, a cut out airbox cover, and a twin-air power-flow kit. I ride at elevations ranging between 5000-10000 ft. my current jetting is a 170 main, a 70S pilot jet, and the HRC needle set to the 4th notch from the top. I have played with many different jet combos over the last 4 years I've owned the bike. This set-up, at least for me, is by far the most power through the entire power-band.

P.S. Once I set up to this jet combo, I do not get de-acceleration pops any more at all.

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An "S" jet is a half step larger than the jet of the same number without the "S". i.e. A 170S jet is a half step between a 170 & a 172...

I understand that the S pilot jets available from Honda have smaller emulsification holes which essentially reduce the size of the pilot air jet orifice. This in turn creates conditions that make an S pilot jet behave like a slightly larger jet then it's fuel metering hole would suggest.

Are you then inferring that an S main jet must also behave slightly larger than non-S main jets? Or have you actually compared the size of the fuel metering hole--S to non-S--and discovered the S is actually larger?? I checked my jets to try and make that comparison myself but I don't have a non-S 158 to compare to the 158S that I have.

I suppose I'm just a little skeptical that the difference between an S and non-S pilot jets supplied by Honda for the XR650R means the same thing for S main jets.

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I just put a 170 main in my xr600 96 and it goes like a rocket but had to go 4 turns out to get it to stop popping on deceleration. Going to work on the pilot jet tommorrow

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A small amount of popping on decel is a good thing,if it doesn't it's too rich.

When the throttle is chopped and the slide closed this when the bike should burble a bit.

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I just put a 170 main in my xr600 96 and it goes like a rocket but had to go 4 turns out to get it to stop popping on deceleration. Going to work on the pilot jet tommorrow

You should probably run a larger pilot if you're 4 turns out on the fuel screw.

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