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dustinw

Which one is the MAJ, PAJ

8 posts in this topic

2007 WR450

I'm uncertain which of the two jets in the bell of the carb intake is the Main Air Jet and which is the Pilot Air Jet.

I assume based on the size & position that the MAJ is the one dead center, and the PAJ is the one to the left. Anyone confirm that for me?

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The jets you are talking about, are located in the bottom of the carb inside the float bowl. Loosen the carb and turn it till you can access the nut on the bottom. Make sure you drained the fuel from the carb and loosen the 17mm nut and you will see the main jet, it is a hex screw with a hole through the center and a 6mm socket will take it out. The pilot jet is right beside it and you will need a thin flat head screwdriver to remove it.

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There is also a starter jet in the bell, it's short and fat, and is also removed with a slotted screw driver. Main jet sizes will likely be in the 165 and up range; Pilot is the 40-50 range; Starter in the 60-70 range...SC

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nah, I'm taking about the air jets, not the fuel jets. The air jets are in the carb bell facing the airbox. I just need to know which is which, hence my q.

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here's a pic (of an older carb, but the positions are the same)

medium.jpg

I think the left one is the PAJ, and right one is the MAJ.

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Oops! Sorry I wasn't paying attention. If you have an OEM 39mm Keihin, then the only air jet you can change is the PAJ. The MAJ is fixed, though it can be drilled and replaced with an adjustable. This was true up through at least '06, unless they changed it for the '07's. If it's the same carb, then there's no use in changing it unless you disable the ACV which basically turns it into a YZ carb. I did extensive work on my '05 carb getting it dialed in and found that the change in the PAJ did nothing except make things worse due to the ACV...SC

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Yeah the 07 has jets slots, and the GYTR kit had me install one in an open slot. I just don't remember which one was in there, and which one I installed.

Right now I have a 70 in the left hole, and a 110 in the right hole.

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The main air jet is on the right side of the bell looking at it from the rear. The 07 does not come with a main air jet stock but the hole is tapped for one. When you purchase the 07 AIS removal/performance/remove the dumb stuff kit it comes with a main air jet that I believe is a 110 size.

Nate

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