Author Topic: KX Jetting... AGAIN!  (Read 7628 times)

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Offline gowen

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KX Jetting... AGAIN!
« on: April 28, 2003, 04:40:29 AM »
Hey Guys,

I seem to be having some jetting issues again. So, here goes, I have been trying my best, but can't seem to get the jetting good. I tried the jetting from the first page, and the bike runs like absolute trash. :-( And I'm unsure why. The low-end is strong, but can't seem to get the RPM's past the mid-range. So, I dropped the neidle a notch, (2nd), it cleared most of the mid up, but the top-end was still rough and very smoky. So, I dropped the neidle another position, (1st notch), it helped the mid-range good. :-) But, the top-end is still way too rich, and I've been working with it, all the way till I'm at a 160 mainjet! What is up with that? Anyway, all is good, except the mid-range is still having issues! It can't seem to get past the mid-range, kinda like fouling out unless you pin the throttle for about 20 seconds, it will break past the mid-range and slam in the top. What is the issue? I have nothing special done, why so little mainjet? What's up with the midrange. Anyway, frustrated. :-) Sorry. Anyway, if anybody has some advice, please let me know, I'm desprate. I'm tapped out on the mid.. I have the air screw at 1 1/2 turns out. I am in 70-80 degree weather, sea level, and not too much humidity, maybe 50%-70%. MAX. Anyway, thanks alot.

Offline Paul

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KX Jetting... AGAIN!
« Reply #1 on: April 28, 2003, 04:54:14 AM »
When was the last time the crank case was pressure checked?

If - I can never remember which one - one of the seals in the bottom is leaking you get a rich condition and if the other is leaking you get a lean condition.

Rick

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KX Jetting... AGAIN!
« Reply #2 on: April 28, 2003, 05:19:41 AM »
Dry side is lean, and will make the crank go bye-bye.  This is especially a problem on the 125's.  So much so, that when my oldest son was consistently finishing in the top 3 in the 125 Expert class in the National Hare & Hound series, I replaced the seal at least once per month just to keep the motor together.  I have also helped a friend resolve a continuing motor failure on a YZ125 with the same fix.  Weird thing.  No mater what we did (new cranks and bearings every time, jugs, pistons, seals and gaskets), the only solution was to keep a fresh seal in place every month.

Fortunately, I have not experienced anything this dramatic on either the 250 or 500.  Good thing, as while you can change the dry side seal on a 125 from the outside, you must split the case on a 250 and 500 to perform the same surgery (on older models, I think you can get to the dry side seal from the outside as well.  Newer models, nope).  Hmmm, kind of makes you wonder why the 125 seal is so easy to change...

If the wet side seal is bad, you can tell pretty easily, as you will have way too much oil in the crank valley.  While this, too, will cause the crank to take a hike, it happens much more gradually.  But, hey, since you have to spit the cases to change the seal, might as well throw in fresh bearing on the crank and rod, along with that nasty dry side seal.

Good luck.

Rick

Offline gowen

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KX Jetting... AGAIN!
« Reply #3 on: April 28, 2003, 12:05:57 PM »
Well, I could test that, but I have about 3 hours on a brand new bottom end, new bearings, tranny gears, rods. Everything mechanical is new down there, except the cases.. :-( I had a professional do it. Just from lack of time. But, anyway, I'd be frustrated if that was an issue. Because it is brandnew. :-/ So, anyway, thanks for the input. I will go about and test it. Thanks, any other suggestions if that isn't the case?

Offline gwcrim

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KX Jetting... AGAIN!
« Reply #4 on: April 29, 2003, 01:05:29 AM »
What size slow jet are you using?
~Crim~
You raise the blade
You make the change
You rearrange me 'til I'm sane

vmxguy25

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KX Jetting... AGAIN!
« Reply #5 on: April 29, 2003, 06:16:14 AM »
Wow!  I cant believe that you are running a 160 main at sea level and it still seems rich.  I have a 1990, and I am running a 160 main and a #52 pilot.....but.....  I am at 7200 feet in Laramie, Wyoming.  There may be something up with your bike. Is the float level incredibly high?

    Just a guess.
 :wink:

                           Gary

DrMojo

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At 800 feet
« Reply #6 on: April 29, 2003, 07:18:24 AM »
Just more data for you.......  I am at 800 feet above sea level and am running a 172 Main with 55 slow and no problems (1 1/2 air screw) when the air temp is above 50 degrees

Here is something to look into.......check the tip of the little float valve in your carb bowl.  The float is connected to it and raises and lowers this little valve as the gas is used.  If this little sucker does not seat and seal properly, your bowl will continue to fill even though your float is bounching off the top of your carb bowl  :shock:

The smallest of parts can reall jam your works!  :evil:

Offline gowen

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KX Jetting... AGAIN!
« Reply #7 on: April 30, 2003, 12:21:23 PM »
Hey, here's the specs:

Carb: Kehin PWK-v886

Mainjet: 160
Slowjet: 45
Neidle Clip: 1st
Air Screw: 1 1/2
Neidle: N0ZE
Slider: #7

thanks guys, this looks real lean, but I don't know the norm.. But, it's acting like it's rich, not lean.. thanks, again, sea level & 70-85 degrees

Offline gwcrim

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KX Jetting... AGAIN!
« Reply #8 on: May 01, 2003, 04:02:28 AM »
You said the needle is on the 1st notch.  You mean the top one, right?
~Crim~
You raise the blade
You make the change
You rearrange me 'til I'm sane

DrMojo

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Oops
« Reply #9 on: May 01, 2003, 04:25:27 AM »
Correction, I am running a 170 main jet.  Not a 172.

Offline gowen

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KX Jetting... AGAIN!
« Reply #10 on: May 01, 2003, 11:35:02 AM »
yeah, 1st notch, meaning the top.. I'm all stumped..
I'm goign to try to purchase a stock neidle I guess.. And bump the pilot to the norm.

91kx

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KX Jetting... AGAIN!
« Reply #11 on: June 08, 2003, 10:17:50 AM »
I had mine totally rebuilt before I even rode it .It had a snapped rod and I got it real cheap.However when I took it out the first time it had zero topend power.It wouldn't rev past the midrange .Turns out my powervalve was not put back together properly.Needless to say it revved.And how  :shock:

QuantumDuck

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KX Jetting... AGAIN!
« Reply #12 on: June 09, 2003, 01:24:43 AM »
I'm gonna back up 91kx on this one,,,Hows your powervalve...I had alot of the same thing you are describing and it turned out to be a powervalve that was WAY out of wack...once that was taken care of...oh my :shock:

and just for the record...I spent time playin with my carb too before looking elsewhere for the problem  :mrgreen:

tomasaki

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KX Jetting... AGAIN!
« Reply #13 on: July 05, 2003, 04:12:48 AM »
I run a 165 main, 58 pilot, 1 a/s, clip at 1st notch.  If I put my clip down any further, it loads up, even with a 48 pilot.