Re-jetting a YZF250 with Slip-on??

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#1
Believe it or not my local dealer could not answer this question.

Would I need to rejet my YZF250 if I mounted an FMF slip-on using the stock header?

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Vic

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#2
Originally posted by rockchucker:
Believe it or not my local dealer could not answer this question.

That might be because he doesn't need to know.

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#3
What do you mean they don't *need" to know?
The pipe was his idea as it was hanging over the bike on display when I picked it up. I'd think if he was making a recommendation that the "dealer" should know what they are talking about.

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Vic

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#4
Originally posted by rockchucker:
I'd think if he was making a recommendation that the "dealer" should know what they are talking about.
Maybe, but they often don't.

What I meant was, he probably doesn't have any experience with that particular set-up and doesn't need to know anything about it in order to sell it. :)
 
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#5
I've got a complete White Bros exhaust on my 250F. When I asked them about jetting, they said no changes and they were right. The bike runs great. No jetting changes were required for my pipe. You might try first with no changes. If still skeptical,call FMF direct and ask them. They'll be glad to help you.

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#6
No changes, it doesn't get any better than that. How do you like your White Bros? Was there a noticeable difference?

Thanks for everyone's info. I'm looking for a topend pipe/exhaust and will probably run the FMF system. If any jetting changes are required I'll document them on DRN.

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#7
I've had trouble getting jetting info out of the dealers here in the Denver area. My son had a YZ125 and it was not jetted properly for this altitude. I called all the dealers in town and not one of them would give me the jetting they were using on their YZ's. Some gave me the run around and some flat out told me they wouldn't because they charge for jetting bikes. One guy told me they misplaced their jetting book. I'm surprised he didn't say that his dog ate it.

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01 YZ250F
00 TTR-125L
00 TTR-90
00 PW-50
 
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#8
Big gains everywhere. Pulls hard on top. White Bros includes the actual dynochart along with a manual and additional info on the unit. It adds around 3hp - 3.5hp throughout ther whole rev range. I don't think there are any losers in the picking of a 250F pipe.They all offer a substantial gain in hp. I'm happy.

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#9
Blake,

What White Bros system did you get, E or R?
I just bought the R4 series which didn't get good reviews from the mags but the dealer made an excellent offer.

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#10
Originally posted by blakemx124:
White Bros includes the actual dynochart along with a manual and additional info on the unit. It adds around 3hp - 3.5hp throughout ther whole rev range.
The Tooth Fairy must have been running the Dyno when those numbers were generated :D



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Rich Rohrich
==

"Wisdom is not a product of schooling but of the life-long attempt to acquire it."
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#11
You guys need to get it out of your heads that jetting is some sort of universal. Calling up a dealer and asking what your jetting should be is a ridiculous notion. Is your bike running the stock pipe, stock gearing, stock reeds, and do you weigh the same as the other rider? All these things affect jetting, so unless you have exactly the same set up and ride the same places as this magical other bike you may not necessarily be getting any closer to what your bike needs. Additionally, all this presumes that the dealer actually has a properly running bike around somewhere, not a good bet.

The real answer is to just learn how to tune your bike.

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Ando
Just another day in Paradise
Two Wheels, Kauai
 
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#12
Rockchuker, We have the R-4 same as you have. I know that this exhaust got bagged on by alot of mags but I am quite happy w/ the pipe. Rich, I know that you are quite knowledgeable. What would be your "ballpark" guess as to how much of a horsepower gain is had with an aftermarket exhaust such as the White Bros R-4? I understand that all the pipe builders are trying to sell their product and possibly exagerate power claims. When I spoke to John Anderson @ White Bros he told me that their dyno is used by MXA and Dirt Bike Mag and that it was considered accurate. The chart enclosed with the pipe was from what I understood to be the same chart (or facsimile) of the dyno readings. You're absolutely right that I can't prove the horsepower claims, and I know that I set myself up for your comment, so I ask you, what would you suggest a person to do when picking a pipe for say, a 250F when you knowingly can't try each pipe and have to rely on looking at a bunch of phony dynocharts put out by the various pipe makers to pick the best one?

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Lorin

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#13
I have a question concerning Ando's statement:
----------------------------------------- Is your bike running the stock pipe, stock gearing, stock reeds, and do you weigh the same as the other rider?
------------------------------------------

Although I understand the idea of pipes and reeds changing jetting, why would the weight of the rider have an affect on it? You tune the engine to run crisp, regardless of weight. You use spring rates to modify suspension for weight and gearing to modify for terrain. Other than possibly jetting richer for something like sand, why would gearing or weight affect jetting? I dont for a minute pretend to know it all, I am just asking for some honest follow up.

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1992 WR 500
If it looked easy, then it wasnt me doing it!!!
 
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#14
Maybe I should have been more clear on the issue. I was looking for "jetting recommendations" as I've had little experience toying the the YZF carbs. There is another reason... Everyone remember when all the mags pumped up every aftermarket exhaust system for the YZF400 upon it release only to recant two years later by stating the stock system was just as good? I don't want to drop $$$$ in exhaust, jetting, and setup if it isn't necessary or won't make much difference. To me, a dealer should be able to answer those questions to some degree if they intend to represent their products accurately. Where else should those of us who don't have years of jetting experience learn, particularily the YZF's?

Blake.. excellent news on the R4. Not sure why the system got so-so reviews. Transworld MX basically said it didnt' suit their needs but maintained it produced noticeably more mid and top than stock.

For those that care.. I got my first taste of the 4-stroke cough in a nasty whoop section last night. Chest still hurts......

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Seth_88

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#15
I learned years ago that my local dealer is of no help whatsoever when it comes to MX bikes. That's why I buy nothing from them except for grips, numbers and minor stuff like that. They didn't even know what kind of jets were used in the 426.

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Seth
00 426