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yamageezer

Jetting question

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Hey guys I need some help with my jetting :applause: I'm a newbie at jetting and to TT. I have a"05 WR450F, done all of the free mods, AIS removed, and removed most of the baffle from the pipe. Now I know these bikes come from the factory running a bit lean, and I have been reading allot of threads about jetting and I have put in a 168 main, 48 pilot, Zip-Ty fuel screw 2-2.5 turns, and a 40 leak jet. I looked into putting in an adjustable pilot air screw, Sudco says can't do it. I still have a bit of a bog on the low end but, once I give it half throttle :banghead: hold on, so I was wondering should I put in a larger pilot air jet and if so what size? Any would be appreciated. :lol::lol:

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James Dean told me this when I asked him about changing my PAJ:

"The WR's have an air-bypass that supplements your stock pilot air jet, unlike a YZ with a #100 PAJ."

I took it to mean it was un-necessary to change it. Anyway, what it does is change the vacuum at the pilot jet. A smaller PAJ creates higher vacuum at the PJ. So if you were thinking of going larger, it basically reduces the amount of fuel that will be pulled through the jet (leans it out). I think it wouldn't help unless it was real hot or real high altitude, although I have heard that certain PJ's work well with certain PAJ's.

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Ditch the stock needle. Either get the JD kit or try a YZ needle (EJP). I run the JD in my 450 and the EJP in my 426. Lots of opinions out there on the best needle. The JD is a bit cleaner but either one will do. Also consider disabling the ACV and putting in a 100 PAJ.

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Thanks BG10459, I guess that's why I did'nt find any posts that talked about the 05's using the pas or changing the paj size. Thanx for your input.

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Thanx PBDBLUE, I did change out my needle to, I believe a 04 YZ needle and I have it set at mid postion, 4th from the top. How did you jet after removing the ACV? I hear it richens the mixture when you do that.

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After removing the ACV you might need to go slightly richer on your pilot jet but a 48 will probably be about right. The ACV is not all bad but it does make getting the jetting right a bit more difficult and IMO contributes to the infamous "bog". Disabling it simplifies things.

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