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Discussion Starter #1
Here's the set-up...



2006 KLX125

150 big bore kit

Stage 2 HotCam

Port matched head

PC exhaust

Top of air box cut out

Screen in

Stock air boot

PWK28 carb

38 PJ

130 MJ

NAPE needle

Clip 2nd from bottom

Air screw 2 out

500ft above sea level 90-100 degrees



So... I just installed this carb after struggling with the VM26-606 for months without being able to get rid of a mi-range bog issue. After some tinkering with this PWK28 carb for a bit, I'm verry impressed and have it running very well mid to top. Much better than anything I ever had with the VM26.



My issue is this... I can start it first kick when its cold. No choke. By cold I mean ambiant temp. When cold, it seems to run great through out, and throttle response is great. As it warms up to operating temp, the bottom end (idle to 1/4 throttle) becomes increasingly "stuttery". Don't know how else to explain it other that it stutters when I. Hold it constant at any given throttle position between idle and 1/4. Then if I kill it, it will only start with choke.



Any help would be greatly appreciated. Thanks in advance.
 

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might want to look in to a rebuild or something along those lines... oil cooler?? or something... sounds like its running lean and getting to hot? make sure u change/and have enough oil in it..maybe a better oil pump? idk i ride 50s and 110s..
 

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Pilot changes and air screw adjustment- make no differance?



What the hell is a nape needle- lol- Might want to order up a small assormtment of needles too jjj, jjg, jjh, and the jjq
 

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Discussion Starter #4
dylancordell said:
might want to look in to a rebuild or something along those lines... oil cooler?? or something... sounds like its running lean and getting to hot? make sure u change/and have enough oil in it..maybe a better oil pump? idk i ride 50s and 110s..


I dont think (hope I dont) need a rebuild. It's pretty new. Now... an oilcooler, yes. I do need one. But again, I dont belive thats causing the problem as it just started when I changed carbs. I'm convinced its a carburation issue.



But thanks for the reminder that I need to upgrade the oil sytem. I just keep putting it off.
 

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Discussion Starter #5
gman said:
Pilot changes and air screw adjustment- make no differance?



What the hell is a nape needle- lol- Might want to order up a small assormtment of needles too jjj, jjg, jjh, and the jjq


I was gonna pm you to get your input knowing you have experience with this carb. Ive only tried the 38 and a 45. Just kinda shootin in the dark and doin what others have done. I have a 42 and a 40 I can try tomorrow. Just dont know which way to go with it. 0-1 turns out... wont run/ dies. 1-3 out... makes little difference. Pretty much the same deal with the 38 and 45. Good when cold, bad on bottom when hot and needs choke to start.



I know, I know... I need the jjg, jjj, etc needle. I just read about a few guys runnin the stock NAPE needle with good luck, so I thought id give it a shot. Maybe thats my problem??? you dont happen to know how the NAPE compares to, say, the JJH do you? Tried looking it up on the sudco chart but couldnt figure it out. I also have an F1340G needle that is deff leaner than the nape, but still dont know how it stacks up against the J's.
 

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Discussion Starter #7
knabb said:
First of all, what kind of PWK do you have? There are many bad PWK copies around. Here is a good thread so you can find out if you need to modify the carb to get it working Keihin PWK copy carb mods - Mini Dirt Bikes & Pit Bikes Forum

Have you tried to change the needle clip?


It is a keihin from a KX85. Not a copy. It appears that all the mods in that link were done on the copy. But that is a great link for those with copies.



Yes, ive changed the clip. Its in the second from bottom position now. That gives me good, smooth mid to top. Didnt seem to affect the 0-1/4 throttle position, only 1/4 - full. But as I stated, I'm still running the stock needle (NAPE). Seems like everyone is running JJJ or JJH.
 

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settintrendz said:
I was gonna pm you to get your input knowing you have experience with this carb. Ive only tried the 38 and a 45. Just kinda shootin in the dark and doin what others have done. I have a 42 and a 40 I can try tomorrow. Just dont know which way to go with it. 0-1 turns out... wont run/ dies. 1-3 out... makes little difference. Pretty much the same deal with the 38 and 45. Good when cold, bad on bottom when hot and needs choke to start.



I know, I know... I need the jjg, jjj, etc needle. I just read about a few guys runnin the stock NAPE needle with good luck, so I thought id give it a shot. Maybe thats my problem??? you dont happen to know how the NAPE compares to, say, the JJH do you? Tried looking it up on the sudco chart but couldnt figure it out. I also have an F1340G needle that is deff leaner than the nape, but still dont know how it stacks up against the J's.


I'm out to a 40pj in the 145SE kit- belive it or not- it would run pretty good the 35 and 38 just would start as well as it should of hot or cold..It pretty senceitive to air screw adjustment now- the pilot is right where it needs to be. Did you have any luck with the 40/42pj?



As far as I know there is no cross refferance compairson between stock factory needles and aftermarket. With out measuring them with a MicroVu or Opictal Comparator.
 

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Discussion Starter #9
Yea, I called sudco today and they said there's no comp chart or anything. Stock needles are specific to manufactures. No way to compare except your way.



As far as the pj goes... I tried the 40 and 42. Still couldn't get it clean. I have a few of these carbs, so I tried another just to rule out a problem with the carb itself. No luck. Same crap.
 

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pretty sure if you go to a jjj or jjh needle it will clean up the bottom some , I'll double check what I'm running, pretty sure it's a 48pj. I know your hesitant to run the pod filter but I hope you just try it to see if it makes a difference. and no you probably do not to rebuild the carb as a earlier poster recommended. I'll post up my jets later.
 

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Just checked my jets, running 42 PJ, 105 MJ, JJJ needle. did you make a step down adapter to get the air boot on the PWK28?
 

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Discussion Starter #12
Thanks kijen. Ill give the pod a try. Ill also try the leaner JJJ or JJH needle. I just cant believe so many people are so lean on the main. Crazy.



Yes, I machined a billet step down adaptor. Wonder if that could be part of the problem????
 

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I have a 38 pj and a 108 main. And a jjg. I have ran this carb on several different builds and runs great. I have to have my air screw out 3-4 turns to run smooth. Rev it up to about 1/8 throttle and adjust the air screw till it smoothed out. People would say my pj is to rich if my air screw out that much but I have tried everything. I have a few friends running the same set up and it's the same way. Try it out hope it works!
 
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