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Urgent question for Carburetor EXPERTS

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At this point I am grasping for anything trying to figure out my carb tuning maladies, even ready to call the local tribal chief for a ceremonial dance!

Seriously, some of you have been very helpful over the past month providing valuable input, but I cant get the midrange and top dialed in.

At this point the only thing that comes to mind is this:

What does the adjusting screw on the throttle valve assembly do?

Is it connected to the TPS?

First time when had the carb opened, I removed the screw and removed the slide. When I put it back together, it all went well – no binding etc. But, I did not pay attention to any adjustment.

With the carburetor in hand and looking at the end that connects to the cylinder, the throttle valve is not completely closed (about 1/8 gap) that can see the daylight through.

Should the valve completely close?

If yes, then can this be part of the problem not being able to get jetting right?

Does messing around with the throttle valve adjusting screw affect TPS adjustment?

Current setup info:

Main jet: 172 (Have tried 165-175)

Pilot: 45 (have tried 48)

Fuel Screw: 1 1/2 turns out (no effect what so ever as to what setting)

Needle: OBDVR raised to 5th clip position (tried 3rd, 4th, 5th)

Grey wire cut

Octopus removed, holes plugged MAJ #100

YZ timed

Clean air filter

Air box lid removed

Stock exhaust with vortip insert


Regardless what jetting combo I am using:

Bike starts first kick

Idles perfect

Midrange sucks (burbling or popping sounds)

Top end sucks (burbling sound)

Also, at midrange, the bike sounds like it is whistling --- more like air scaping through a hole. is this an air leak???

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from the front of the carb (engine end) the slide shouyld be completely closed.

the tickover/idle height is about 5 or 6 turns out from closed.

you must make sure that your slide plate is in THE RIGHT WAY UP!! it's possible to get this wrong.

try going down 5-10 on the MJ and then go up 1 or 2 times on the needle.



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I just checked, my main air jet is #65, i thought it should be # 200??

The MAJ is (when you are looking at the carbs end)the one on the right???

This is the way it came from factory---


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The MAJ was a typo in my first post. I changed PAJ to 100.

The only thing that I can think of is that 2 weeks ago when I had the carb apart i mixed up the PAJ 2 with the MAJ, if that was the case then, the MAJ in bike was # 160. ( The MAJ has a flat head???)

The part that is funny here is that alot of people complain about the hardship in starting the WR. No matter how I have screwed up the carb on my bike- it always starts the first kick!!

At this point, it looks like I have a problem on the top, cant tell if it needs to be larger than 175 or smaller than 165.


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as i said

go down 10 on the MJ and then if ok start lifting the needle one at a time.


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Hey Taffy,

Your advise over the past couple of weeks have produced the best results so far.

I think that i am getting close to some sort of happy ending here.

The best setup so far:

45 pilot

65 pilot air jet

Needle at the 5th clip position --- this is the best bang for the pain so far - very crsip and sharp response

175 main

Fuel screw at 1 1/2

Still kind of bogin/burbbling on the very top.

MAJ was # 60, all i have at home is #160. I thought from the factory it should have been #200


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I cant imagine how it works if you really have a 65 in there as a MAJ. MAJ stock is 200. Yeah its on the right. PAJ is the one on the left.

Let me hypothesize what you may have done, having re-read your post : De-octopssuing requires a 100PAJ to be installed. You said you have a 100MJ in your first post!! Did you remove your MAJ and install the 100 PAJ in the MAJ orifice and leave the PAJ at 65 ? 65 sounds low for what your PAJ should be - ask someone else for recommendation.

PAJ is on the left, MAJ on the right.

If you have no manual....get one, parts location etc... its all explained and there are lots of pictures/diagrams.

The carb slide is a common problem....it is easily installed up side down if you dont pay attention to the dismantling.

Whenever I dismanlte ANYTHING until I am familiar with it I always lay the dissasembled parts spread out in the general visual order they fit back - sort of like a parts diagram.

anyhow good luck

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