Jetting!!! Again and again and again!

[KXcam22]

Slow,
  172 seems rich, even at your altitude of 1300'.  The 55 is about right possibly a touch lean for colder weather.  I need more info:

1. What is your needle and clip position?
2. Type of riding
3.  Plug heatrange and type.
4.  premix Oil brand and mix ratio
5. Perfomance modifiations.
6. Is the float level set correctly.

Cam.

[atrain40]

my bike had stock jetting with 168main/60pilot and ran good at 1000-2000ft but seemed to splooge a ton and seemed like it was a little rich and didnt have that topend punch. so i changed the main to a 162 and pilot to 55 seems to have more topend zing. and i will test it out this weekend to see how it runs and if the splooge stops i mix it at 32:1 and like to put enough oil in the gas to be safe. will probly lean the main out more when i go to kennedy meadows which is 7500-9000ft in elevation but dont know how lean. thanks

[slow600]

Slow,
  172 seems rich, even at your altitude of 1300'.  The 55 is about right possibly a touch lean for colder weather.  I need more info:

1. What is your needle and clip position? not sure needle type, second clip from top
2. Type of riding. street legal supermoto
3.  Plug heatrange and type.  standard ngk
4.  premix Oil brand and mix ratio. belray 50:1
5. Perfomance modifiations. kips bolt, pc platinum 2, pc silencer, window piston, thin head gasket.
6. Is the float level set correctly. float set correct

i obviously wasnt fully prepared for this, thanks for the help. my gut says go down on pilot to resolve hot start issue, gonna go back to 170 main since it seems to run stronger that way.

[matzilla]

I recently thought I had a jetting problem when I noticed my 88 wasn't running right at higher RPMs. It has warmed up here a lot lately, and when we put it together recently we jetted it a bit rich just to protect the shiny new parts during break in. I actually used Dumonde Tech break in oil. It still ran great at low RPMsn but would sputter and dog out up high. I thought for a minute about the plug, but figured if it was fouled it wouldn't run at all. After talking to a friend I changed the plug and what a difference! Cleaned up completely. Runs great again. The pilot was a bit rich, but with some minor air screw adjustment is much better too. I just wanted to share what I learned about how a fouled plug will still run, just not efficiently.

[500freak]

hi guys.. i was looking at some of the jetting charts on here and seen that my carb i way out. it has a kiehin pwk with a 162 main and a 50 something pilot jet with the clip on the 1st notch. but the bike actually loads up on the bottom end.... what gives??? after starting and warm up it takes to 3rd gear to clear out. even when its hot if you idle down a long hill it will load up alittle. i mix it 40-1 with amsoil full synthetic for power valves with 110 mixed 50/50.  any one have any idea....

[Friar-Tuck]

   500,
 There's a couple things right off that might be affecting your jetting.
   Air filter clean & Oiled properly.
   Float level set correctly.
   Is the choke working O.K.
   Crank seal drawing in tranny fluid.
   Has the Carb Body been bored out.
   Has anyone modified the main jet or is it a real Keihin.
   Has the needle been modified.
    Are the reeds in good shape ,  if they are not lying flat (Closed) there could be a tendancy for air to actually flow back and forth through the carb and pick up additional fuel.
     Has the cylinder been bored out to a larger size.
  Well, Right off this will give us some more info to track down this buggar...
     Tuck\o/
 

[500freak]

i did a full rebuild on the engine about 10 hrs ago, so i know the seals are good. the carb isnt bored and the float setting is fine. the choke works fine, when you pull it when its warm it revs then loads up. it is bored to 86.5mm and ported. the reeds are new boysen two stage. it had the stock carb on it running 1 seize bigger main jet. i got the keihin off of a cr and had to adjust the needle leaner with smaller jetting, and it runs rich.... the plug after running is brown and has some oil left on it. 

[Friar-Tuck]

  500,
   Thank you for a bit more info.
  The Cr's come with a Keihin PJ,  is that the model your running on the bike?
        (the jet and needles are interchangeable w/the PWK 39.5,38,38 Air Stryker and PJ)
    The PJ's idle circuit it tied in to the choke.  Do you rotate the choke knob for the Idle adjustment?
    Tuck\o/

[RM_Rider14]

Anyone live in Colorado or ride at these elevations?  I am trying to find out what your jetting is if you do.  I have my YZ 250 dialed in for elevation and I'd like to get the KX 500 too.

  TIA-

[500freak]

no the choke doesnt adjust idle.

[Friar-Tuck]

 500,
  The PJ's Idle circuit is Tied to the choke. I'll try to find an illustration.
  The bottom of the pj carbs choke looks like #13 in the diagram.
       https://www.justatv.com/pages/keihin_pj_parts_diagram/pj_par6.gif   
  As you rotate the choke knob it should increase or decrease the idle.
If you have an Idle screw that lifts the slide we will have to determine just what exactly you have.
  This is the PWK
    http://www.sudco.com/Diagrams123/exppwk.gif
Note the choke knob assembly #2 and the idle screw #29 ( which is absent in the PJ )
   Do you have the screw type Idle adjustment?
  Tuck\o/

[500freak]

the idle adjust isnt the choke. it has a adjuster screw, the carb came of a 95 cr, and as far as i know its a pwk.

[Friar-Tuck]

  500,
 The Cr's all came with 38mm PJ's from the factory, You do, I believe have a PWK.
   I am also led to believe it is either a 38mm or 38mm air stryker.
  There are some markings on the side of the carb body near the where the float bowl attaches.
   If possible could verify that nomenclature. It should have PWK and some letter /number combinations.
     And if you happen to have the carb off sometime, measure across the opening that goes in the engine side airboot.  That will tell you the actual mm.

   The smaller carb has a greater air velocity than a larger  one.   That's why your jetting appears to be so lean.
 (Or at least for a 39.5 PWK)   

  The Jetting you currently have is not all that far of a PWK air striker I bought and put on my CR for singletrack / Woods riding.
     If you snoop around CR500Riders.com and search air stryker in the tech section this info should pop up.
( Those guys were also concerned about the small jet sizes)

 If it ain't broke don't fix it my grandpa used to say.
 I know it did make a noticable difference on my CR.  However I don't have a lot of WOT riding here to notice any loss of top end.
  I was more worried about hanging on!

  I have no doubt you got the carb off the CR.  How it may have got there...may be another story.
    Tuck\o/

[500freak]

well... this is what i came up with. it says pwk-j755-fg31 and it measured 39.5mm. i usually run half to WOT. it just sounded way off to me, and i didnt want to melt the piston down. thanks for the info.

[98kaw500rider]

Hi guys , I just picked up a 98 kx500 that has been sitting for the last 3 years. Got it really cheap with a title but i don't know much about these big bores except they are monsters. I cleaned the carb out , new plug , fresh gas. It has a fmf gnarly gold series pipe on it and uni air filter ( no lid on air box ) and i live in Ohio . The jet in it now is a 172 , does anyone know if this should have a bigger jet in it due to the pipe ? ? Also i have mixed 3 oz. of klotz R50 to 1 gallon of 94 ( thats what a local shop told me to mix ) and it seems really rich in a heated garage. I don't really plan on riding it until it warms up , it's only 25 degrees here now. Any help would be great ! Thanks