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post #1 of 1 (permalink) Old 01-17-2006, 09:58 PM Thread Starter
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Why do the majority of dealers and independant wrenches tell people
they have to re jet or remap if Fi when they change pipes ?
I think that is one of the most asked questions of not only me
personally but on here and some of the other forums I frequent .
Is it for added money or some sort of CYA thing ???
Anyone know ? Cos I think we all almost agree it ain't needed justfor a pipe change
Perhaps it's because most aftermarket pipes do change backpressure and some adjustment is needed. I think most dealers are trying to expose their liability

I think it harkens back to the days of 2 strokes...whose exhaust
was something left to be desired. Changeing pipes meant the need for
power..and most times accompanied trashing the stock air box for a
set of K+N's..which needed a richer fuel mix. I guess through the
years it just got confused and when someone said they were getting
new pipes...they figured they needed to re-jet.
Our bikes do burn lean...a small step in richness could not are adding pipes for power...not sound quality..which
seems to be the vogue now.

With independent wrenches, I think it is a money thing.. When most people (that don't know any better) hear the word re-jet, the firswt reaction is "Oh Hell, I don't do carbs"... "Not a problem" says the wrench, "I can take care of that for you, just leave your wallet and a pint of blood on the counter"... I've noticed that no one has ever pulled that crap on me, but I look like a grungy grease soaked biker, and they guess (correctly) that I know better..

Jets and the ear shave

(See Ear Shave)

Poking around in the files section, I found this under Trent's ear shave: "With a lot of help from Illigit, Wired George, a lot of others, I finally gor her running where I liked her. I still tweek with it for fun, but the basic recipe I came up with was no washers, 42 pilot jet, about 145 - 150 rear carb and about 150 -155 front carb." So he is saying the FRONT carb should have the bigger jet, not the rear. I have no clue which might be right, or why. Any thoughts? I seem to be doing fine with 140 in both. Should I change? I'm afraid it will kill my gas mileage if I go bigger... Would I have more power, or would it just start flooding out? Pick
You know, I really should stay out of this, since I havn't done the earshave myself. That said, the guys at Sherm's (which is no longer owned by Sherm Accord, a VROC member) recomend the 140/142 combination IIRC. But if you are running right, why fool with it??? Legend has it that the rear cylinder runs hotter than the front and perhaps that explains the difference (tho' the 140/142 vs. 142/140 is counter-intuitive to me). HELP!!! Somebody who REALLY knows carbs want to weigh in?? grambo
The jug that runs hotter should have the bigger jet..There is not alot of diffrence really in a 140 and a we are not talking that much richer in the rear..and that's if the engine is run hard. If the plugs look good and the bike pulls fine through out the rev band..a bigger jet may not be needed. There is a point where most will stop and it usualy is on the lean side. Going a bit richer may give you a tad more power..but you'd be hard pressed to feel it. Shaving a whole secound off a lap time is alot on a race track..pretty meaningless on the street. got that extra secound..but your MPG of course will suffer. If your bike runs great Jim..DFWI Knifemaker
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