All 2st Jetting Chat - Need Help? Post Your Questions Here

[windsurf]

On the jd reds you guys get how many lines are on it?

I guess you mean clip slots? There are 5 on red and blue.

 

[lankydoug]

Year & Bike Model = 2009 WR250
Carb = Mikuni
Pipe & Silencer =Stock
Other engine mods = none
Premix ratio & fuel type = 40:1 and 91 octane no alcohol pump gas.
Temperature range (deg F) = 55 degrees F humidity 43%
Elevation (feet) = actual altitude is 900 ft. air density altitude is usually between 1500ft and 2500ft in this area but I have seen 3500 ft air in the humid summer.
Main jet =390
Pilot jet = 35
Needle = E16BFY43-74 stock
Clip position = middle or 3rd from top
Air screw setting = 1 1/2
Slide = stock
Conclusions/Results = Crisp and responsive all the way through, air screw is very responsive 1/2 turn makes a big difference. At wide open in 5th gear it flattens out just a hair but this is at 70 mph which I will never come near in the woods. The flat spot would probably come out with a 385 or 380 main but I don't have one to try and it only does it in lower gears when you are late to shift.

I tried dropping the needle 1 clip but it would lean ping or rattle at certain part throttle positions. If I was at a higher altitude I think 2nd clip would be perfect.

I'm still not sure why everyone is avoiding the Mikuni, it's been good to me so far.

Ok this is an update. With the 390 main in I felt there was still something left but was afraid to go leaner because it was feeling like the 91 pump gas was on the edge of detonation. I bought some Sonoco 110 and mixed it 50% with 91 and leaned the main out to a 380. This is a better set up and will be a lot better in the heat of the summer when the air is not as good.

I need to ride a few other bikes to get a comparison but the bike pulls so hard off the bottom and all the way through I can't help but wonder what a 300 is like.

Next step, get a tall seat and the suspension done so I can get to the standing position quicker and stay on it.

 

[TROFFER88]

try a keihin

 

[lankydoug]

Year & Bike Model = 2009 WR250
Carb = Mikuni
Pipe & Silencer =Stock
Other engine mods = none
Premix ratio & fuel type = 32:1 and 91 octane no alcohol pump gas Motorex oil
Temperature range (deg F) = Missouri ?
Elevation (feet) = actual altitude is 1000 ft.
Main jet =440
Pilot jet = 45
Needle = "Gay Needle"
Clip position = middle or 3rd from top
Air screw setting = Stock ?
Slide = stock
I purchased new Pilot jet, Main jets and the new needle from Hall's Cycle thru Clint. I was having problems with being to lazy thru bottom to middle RPM, so I talk to Clint and he told me to rejett it so I did. It fix it, but now I'm having problems with it after I've been running it for a while it does't want to start if I was to kill the motor. I started with the clip in the 3rd position then I drop it to the 4th position and still does the same thing. If anyone knows what it could be please let me know.

My 09 WR250 was hard to start until I leaned it out. The plug got progressively more fuel fouled until it was impossible to start. Now mine has been starting 1st kick hot or cold.

 

[utopia]

corey43,
I think your pilot is too rich. Try a 35 pilot with GAY needle in 4th. I'm at 6000 ft and using 30 Pilot, Air Screw out 1 1/2 turns, and GAY in 3rd and it works really good.

 

[corey43]

Ok, Thanks Guys! Hopefully it works.

 

[lankydoug]

corey43,
I think your pilot is too rich. Try a 35 pilot with GAY needle in 4th. I'm at 6000 ft and using 30 Pilot, Air Screw out 1 1/2 turns, and GAY in 3rd and it works really good.

+1 on the 35 pilot. Please repost when you get the 6000 ft jetting sorted as I will be riding in CO at about the same elevation someday and would like to know what you come up with.
I don't know about the other bikes like the 125s but the stock Mikuni with the stock needle is working great on my 09 WR250.

 

[utopia]

+1 on the 35 pilot. Please repost when you get the 6000 ft jetting sorted as I will be riding in CO at about the same elevation someday and would like to know what you come up with.
I don't know about the other bikes like the 125s but the stock Mikuni with the stock needle is working great on my 09 WR250.

I will hopefully get to do some testing this weekend when I drive east a few hours to get away from the snow.

 

[corey43]

So where should my air screw be at.

 

[lankydoug]

Year & Bike Model = '09 WR250
Carb = Mikuni TMX38
Pipe & Silencer = Stock
Other engine mods = None
Premix ratio & fuel type = 40:1
Temperature range (deg F) = 55-60F
Elevation (feet) = 5,500 ft
Main jet = 360
Pilot jet = 30
Needle = Stock BFY
Clip position = 2nd
Air screw setting = 2-2 1/4
Slide = Stock
Conclusions/Results = I had tried all main jets from 390 to 460 and the power still dropped off at the upper end. Against conventional wisdom and service manual recommendations I kept going down on the Main (partially inspired by lankydoug's results). It gradually revved further out until with the 360 it revved all the way and now has good power and runs clean throughout the range. I think I will try a 350 because it is still a little on the rich side. The BFY needle in the 2nd position is also just a little rich. Last summer I had really good results with the GAY needle in 3rd position with AS at 1 3/4, so I will be going back to that. I have about 30 hrs on the bike and have not checked the powervalve setting yet. Since I got it running good I probably won't pull the top end apart until I need to. I also have a 36mm PWK that I plan to try this season.

That is what I expected my settings to end up like at your altitude although I doubt the 350 main will work until your above 8000 ft. I might add that I like mine set a hair on the rich side to smooth out the transitions between circuits and keep from going lean on those really cool dry good air days.

 

[lankydoug]

Year & Bike Model = '09 WR250
Carb = Mikuni TMX38
Pipe & Silencer = Stock
Other engine mods = None
Premix ratio & fuel type = 40:1
Temperature range (deg F) = 55-60F
Elevation (feet) = 5,500 ft
Main jet = 360
Pilot jet = 30
Needle = Stock BFY
Clip position = 2nd
Air screw setting = 2-2 1/4
Slide = Stock
Conclusions/Results = I had tried all main jets from 390 to 460 and the power still dropped off at the upper end. Against conventional wisdom and service manual recommendations I kept going down on the Main (partially inspired by lankydoug's results). It gradually revved further out until with the 360 it revved all the way and now has good power and runs clean throughout the range. I think I will try a 350 because it is still a little on the rich side. The BFY needle in the 2nd position is also just a little rich. Last summer I had really good results with the GAY needle in 3rd position with AS at 1 3/4, so I will be going back to that. I have about 30 hrs on the bike and have not checked the powervalve setting yet. Since I got it running good I probably won't pull the top end apart until I need to. I also have a 36mm PWK that I plan to try this season.

Today in MO I went to the 370 main and it pulled harder at high rpm and didn't lose any mid-range pull. On another note I played around a little with the float level and found out that if you get it too low it runs completely erratic. Special attention must be paid to the clip that retracts the needle from the seat, if there is too much play I think the needle might stick a little and cause the fuel level to drop too much before it opens, causing it to go lean and get behind until you lift off the throttle. The spring loaded needle is not my favorite set up to get an accurate setting so I went as far as blowing through the fuel inlet line while raising the float manually to get the exact height that the fuel is shut off.

 

[Bill502]

I purchased a used Keihan PWK A/S for my 167 and the top has no threads in it. Does any one know the size/ pitch for the threads that are on the cable guide so I can get a tap? Sorry if this post is in the wrong place.
Thanks Bill

 

[LawnDartMike]

Would a low float cause the bike to load up on small down hills? I have the jetting dialed in with a tan plug after a plug chop and it runs clean low-top. But after a short down hill it loads up and takes a bit to clean it out. I've also noticed that it drips gas if the bike is anything but straight up.

 

[lankydoug]

Would a low float cause the bike to load up on small down hills? I have the jetting dialed in with a tan plug after a plug chop and it runs clean low-top. But after a short down hill it loads up and takes a bit to clean it out. I've also noticed that it drips gas if the bike is anything but straight up.

A high float will cause that.

 

[LawnDartMike]

High is right. I guess I was thinking of holding the carb upside down. I lowered it and rode today with no real change. Guess I just need to ride it harder. But at least the dribbling stopped.

 

[Vinduro]

I am still running the Keihin PWK 36mm Air Striker from the 2011 KTM 150XC. I am running the 170 main jet (Stock), 6.0 slide / throttle valve ( stock is 7.0), NOZH needle in the #2 position (Stock NOZI #3), and a 35 pilot jet. I had to adjust the Air Screw out to 2.5 turns.

 

[Xcuvator]

Here comes my settings for my WR 300 2010. I have used the racehead in the winter, but i jet the same without it.Iit was too much with the racehead in the woods, so i removed it for the summer. I also have a Leo Vince silencer, but that doesn´t affect anything.
Sealevel to 300 meters above and around 15-25 degrees Celsius
Keihin PWK 38 AS with slide 7
JD red needle in lowest (leanest clip position
175 main jet
40 pilotjet
Airscrew 2-21/2 turns out depending on temp
The bike runs very clean, don`t spooge at all, rolls very smooth on idle and starts at first kick almost every time. I like to go quite lean in the gnarly stuff as it makes the bike smooth on throttle and doesn´t make me tired. And when i´m tired i can still get a smooth powerdelivery. I don´t think a lot of bottom end power always is good. It´s strong enough anyway! If it´s jetted richer i get a bludder when i open the throttle and then a sudden powerdelivery when it starts to run clean, and as it is now it is very smooth all the way.
Johnny

Hey Johnny,
I know you have been working on your settings a long time. I am one notch richer with my red needle on my 250 and the same pilot 1 1/4 turns. My bike idles high when I stop. I like the way it runs but I'm worried it's a little lean. Does your bike idle right down?

 

[Johnnymannen]

Ok. Yes, my bike goes down on idle as it should. Maybe you are slightly lean on your pilotjet. As it idles high with the airscrew quite a bit close to lowest setting i would try to go up one size on the pilot (42) and maybe around 2 turns out. You don,t have to worry about it running lean on idle. You won,t damage anything. What happens if you turn the airscrew 1/2 turn in just to see what happens?
Johnny

 

[Xcuvator]

Ok. Yes, my bike goes down on idle as it should. Maybe you are slightly lean on your pilotjet. As it idles high with the airscrew quite a bit close to lowest setting i would try to go up one size on the pilot (42) and maybe around 2 turns out. You don,t have to worry about it running lean on idle. You won,t damage anything. What happens if you turn the airscrew 1/2 turn in just to see what happens?
Johnny

What you say makes sense. What I don't understand is why you and I are so lean. We are way leaner than the JD recommendations. After top notch red, there is no place to go leaner. I ride that bike at 2000-2500". If I had to ride higher, I would probably need to get a different needle.
I had to raise notches on the red needle after I had my squish set along with combution chamber reshape and RB designs carb divider plate. I guess there is just way more signal?

 

[lankydoug]

Year & Bike Model = '09 WR125 to 144 eg
Carb = Mik (stock)
Pipe & Silencer = Stock/ stock arrow
Other engine mods = 0...rock stock inlc. air filter.
Premix ratio & fuel type = 40:1 putoline
Temperature range (deg c) = 10-28
Elevation (feet) = 1500
Main jet = 480
Pilot jet = 35
Needle = factory needle
Clip position = #4
Air screw setting = 1.5 - 1.75 out
Slide = 4.0

Runs very well and has a nice safe over rev! don't know what all this pwk conversion is about no need i say NO NEED! The bike rips and handles and stops, perfect......................

I feel the same way about my 09 WR250