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A little Jetting Interpretation help please

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We both own the 05 wr250f's and we are comparing the jetting (same carb's) to the previous years and it looks like the 2005's are lean on the high end.

Here is a quote from Rich with his analysis:

"The only thing significantly different from the '03 WR, YZ, and '05 WR is

the main jet. It would be helpful to get a copy of (or take a look at) the

'05 YZ manual to see how it compares.

Our main jet is WAY leaner.... we're at 168. '03 YZ was at 178, '03 WR was

at 185, '03 WR non-US was at 172. This does not make sense. What would

make sense would be if the non-US were at 185 and the US were at the leaner

172, but either way, we're leaner.

Our pilot jet is the same at 40.

No way of knowing on the needle jet... the part numbers are different for

all three, except that the part numbers for the '03 WR European match the US

'03 YZ, and use the same part standard.

That's the deal with our manual being split... the top set of numbers for

the jet needle is US, the bottom is European.

The leak jetting is close... we're all at 90-100 "

Any thoughts / opinions on this? Are the 05's really lean on the top end? 😢 We have not yet made the mods (going to start soon), but right now the bike has no top end in 5th gear. I am wondering if we make some of the mods will it make us lean, since we appear to be leaner than the previous years. And mostly I am interested in general opinions on the differences.

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You made the mistake of mentioning Rich in your post. It would be a mistake to think something different than what he does.

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yammies have always been sensitive to epa regulations. they come stock lean so any random testing wont show gross readings of the unburnt gasses.

Now go ask JD what he thinks. You wont have to pay for his answer. 😢

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thanks, I'll never mention Rich again. 😢

He actually has a high IQ and will catch on quick, but I agree he should not really be giving advise since he has only riden a bike 3 times in his life, and so far has made no mods coupled with almost zero real world experiance ... 😢 LOL.

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He's thinking of a different Rich... there's another one on here that I've seen.

I haven't been around long enough to be famous yet... and I don't THINK I've pissed anyone off 😢

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Couple of things to keep in mind that came to me this afternoon....

1 - The YZ has different exhaust cam timing... that will affect jetting.

2 - Each of the above described bikes uses a different part number for the needle.

A different needle can have a different diameter or different taper. This will affect the size of the main jet needed to hit the same mixture at a given throttle opening.

They very well could have leaned out our '05s, but unless we swap in a needle from an earlier model, we can't compare the jet numbers directly.

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