Issues with PWK on KX125

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4/24/2020 11:43 AM

Hi
I Have a KX125 2004 with a pwk airstiker 38, have som jetting issues...

Engine specs
Bud Racing top
Boyesen intake
Mildly ported
Pro circuit
Aspen R 102

I cant get the bike to run good on low throttle.

Went from 38/160 #7slide step by step to 65/190 #7 slide, the bike runs ok but not good.

No airleaks and newly built engine.

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4/24/2020 12:26 PM

Wangstedt wrote:

Hi
I Have a KX125 2004 with a pwk airstiker 38, have som jetting issues...

Engine specs
Bud Racing top
Boyesen intake
Mildly ported
Pro circuit
Aspen R 102

I cant get the bike to run good on low throttle.

Went from 38/160 #7slide step by step to 65/190 #7 slide, the bike runs ok but not good.

No airleaks and newly built engine.

What needle are you using ?

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4/24/2020 12:34 PM

digger wrote:

What needle are you using ?

Im not sure.. :/

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4/24/2020 12:52 PM

Wangstedt wrote:

Im not sure.. :/

Before I can offer any meaningful advise I would need to know what it is. It's the most important jet in a PWK. Everything else gets tuned around it.

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4/25/2020 11:35 AM

I think your slide is way too big

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4/26/2020 3:18 AM

Bruce372 wrote:

I think your slide is way too big

What slide do you think I need?

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4/26/2020 9:37 AM

Bruce372 wrote:

I think your slide is way too big

Wangstedt wrote:

What slide do you think I need?

I ran a 4 slide on a rm125 using a screw top pwk back in the day.

Not sure you should go that rich though, but it does look like you've gone mega rich on the jettinf to compensate for a lean slide.

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4/27/2020 5:54 AM

It really depends on which needle you are using. There are needles that will allow you to use a #7 slide, but more realistically I would recommend something closer to a #6. A #4 slide is very, very rich when used in a pwk.

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4/27/2020 5:55 AM

digger wrote:

It really depends on which needle you are using. There are needles that will allow you to use a #7 slide, but more realistically I would recommend something closer to a #6. A #4 slide is very, very rich when used in a pwk.

Its a PWK Airstriker 38mm QAS new. Do you know wich needle i could use without changing the slide?

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4/27/2020 2:38 PM

I would try using a single taper CCL needle. Start out in the #3 clip position with a 45 pilot and a 165 main jet, and the air screw at 1.5 turns out to start with. Also make sure the float height is set correctly. I'm not sure which version of PWK you have.

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5/1/2020 11:14 AM

You can keep busting your head trying different needles and slides, spending a fortune, or you can spend $15 on a jetting calculator and let it show you what slide and needle work best.
www.dragonfly75.com/moto/carbjetting.html

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www.dragonfly75.com/moto/ all about 2 Stroke technology, including calculators

5/6/2020 4:17 AM

I used a 97 KX250 carb with 38/158 jetting.

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04 KX125
94 KX250SM
75 Z1-900

6/2/2020 11:06 PM

So i got some more info now.
The throttle is marked 65, is it the slidenumber?
The needle is marked DGN.

/ Wangstedt

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6/2/2020 11:35 PM

normally you arrive at the right slide cutaway (in millimeters) by dividing the carb size by 10. So yours should be 3.8 or 4mm, but instead it is 7. That will lean out the low range jetting too much.

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www.dragonfly75.com/moto/ all about 2 Stroke technology, including calculators

6/3/2020 12:46 AM

jaguar57 wrote:

normally you arrive at the right slide cutaway (in millimeters) by dividing the carb size by 10. So yours should be 3.8 or 4mm, but instead it is 7. That will lean out the low range jetting too much.

So even if its marked with 65 its a slide #7?

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6/3/2020 11:35 AM

Wangstedt wrote:

Hi
I Have a KX125 2004 with a pwk airstiker 38, have som jetting issues...

Engine specs
Bud Racing top
Boyesen intake
Mildly ported
Pro circuit
Aspen R 102

I cant get the bike to run good on low throttle.

Went from 38/160 #7slide step by step to 65/190 #7 slide, the bike runs ok but not good.

No airleaks and newly built engine.

digger wrote:

What needle are you using ?

The needle is marked DGN

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6/3/2020 2:57 PM

take the needle out of the slide and let it rest on a flat surface and measure how many millimeters high is the highest part of the cutaway. For a 38mm carb it should be close to 4mm. read this guide to jetting: http://www.dragonfly75.com/moto/carbtuning.html

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www.dragonfly75.com/moto/ all about 2 Stroke technology, including calculators

6/3/2020 3:41 PM

jaguar57 wrote:

normally you arrive at the right slide cutaway (in millimeters) by dividing the carb size by 10. So yours should be 3.8 or 4mm, but instead it is 7. That will lean out the low range jetting too much.

Wangstedt wrote:

So even if its marked with 65 its a slide #7?

No it's a 6.5. pretty common slide size. Ignore what this dude is telling you. Jetting by a calculator is a recipe for disaster. 6.5/7 should run just fine in a 125 with correct brass. I'll look when I get home and see what we were running in CR125 before I threw STIC in it. It might get you close..........

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6/3/2020 4:17 PM

What I said was due to what I have noticed with most carbs. There must be a reason for that general rule. I'm not saying perfect jetting is impossible if the cutaway ignores that rule though. I'd have to analyze it on my jetting calculator. It probably has some relation to the clearance between needle and needle jet.

World Championship testimony: Thomas in the Nethlands wrote about the results of using my jetting calculator:
"Just some nice input about the bike (1965 Husqvarna 360 piston port with a Mikuni 32) that I sent you info on earlier and you corrected my input, and sent new corrected one to me, and where red line was rather straight and nice. I was just informed that that bike (driver said jetting was great on the sand track) was one of the bikes in the Swedish team winning world championship in Netherlands yesterday (Sept 21 2019) for vintage bikes before 1965 and driver was over 72 years!"

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www.dragonfly75.com/moto/ all about 2 Stroke technology, including calculators

6/3/2020 4:18 PM

another testimony:
"This software works very well for carb jetting. It gets you into the ballpark and is almost spot on first time. I setup 2 bikes (CR250 and a CR500) with it and afterwards only had to do some minor adjustments with the air screw. Keihin PWK 38mm Airstrikers on both bikes. It helped in the selection of the needle, main, and pilot. You could try different combinations and it would show you if the combo was too lean, rich, or on the money. I took what I learned from the information and put it into the bike and it worked very well."

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www.dragonfly75.com/moto/ all about 2 Stroke technology, including calculators

6/4/2020 3:32 AM

Tracktor wrote:

No it's a 6.5. pretty common slide size. Ignore what this dude is telling you. Jetting by a calculator is a recipe for disaster. 6.5/7 should run just fine in a 125 with correct brass. I'll look when I get home and see what we were running in CR125 before I threw STIC in it. It might get you close..........

Thank you ! smile

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9/2/2020 10:56 AM

Still not getting the bike to run good...

JD jetting red needle taken down 0.1mm or else it wouldnt run at all.
Got the #6.5 slide 45/180 jetting.

Tested the #5 slide aswell but it didnt work, the bike keeps bogging.

Getting kind of tired of this and got no ideas. have like 1 hour on this bike the whole season.


Still no leaks and the exhaustvalve works as it should

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9/2/2020 11:25 AM

Wangstedt wrote:

Still not getting the bike to run good...

JD jetting red needle taken down 0.1mm or else it wouldnt run at all.
Got the #6.5 slide 45/180 jetting.

Tested the #5 slide aswell but it didnt work, the bike keeps bogging.

Getting kind of tired of this and got no ideas. have like 1 hour on this bike the whole season.


Still no leaks and the exhaustvalve works as it should

Did you try the needle and specs that I suggested, CCL needle, 48 pilot and 178 main ? They should work with the 6.5 slide best.
What JD jetting kit did you get for your bike ? The small bore JD kit should have needles that have scribe lines under the last clip groove, if not you may have the wrong needle kit.

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9/2/2020 11:29 AM

Wangstedt wrote:

Still not getting the bike to run good...

JD jetting red needle taken down 0.1mm or else it wouldnt run at all.
Got the #6.5 slide 45/180 jetting.

Tested the #5 slide aswell but it didnt work, the bike keeps bogging.

Getting kind of tired of this and got no ideas. have like 1 hour on this bike the whole season.


Still no leaks and the exhaustvalve works as it should

digger wrote:

Did you try the needle and specs that I suggested, CCL needle, 48 pilot and 178 main ? They should work with the 6.5 slide best.
What JD jetting kit did you get for your bike ? The small bore JD kit should have needles that have scribe lines under the last clip groove, if not you may have the wrong needle kit.

I totally forgot that. Ill order one immediately.
I might have the wrong kit then...

Ill get back to you.

Its the PWK Airstriker 38mm QAS Shortbody

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9/2/2020 11:33 AM

That the correct carb for your bike. JD sells a kit for small bore bikes,125/150 and one for 250/300 bikes. The kit for the larger cc bikes will not work in your 125.

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9/2/2020 11:37 AM

digger wrote:

That the correct carb for your bike. JD sells a kit for small bore bikes,125/150 and one for 250/300 bikes. The kit for the larger cc bikes will not work in your 125.

It was one for a 500...

So I ordered the CCL now.

Hope this will work smile

Thank you !

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9/2/2020 3:01 PM

Wangstedt wrote:

It was one for a 500...

So I ordered the CCL now.

Hope this will work smile

Thank you !

I meant the short body PWK. The internal jetting is easy enough to change.

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9/3/2020 12:46 AM

digger wrote:

I meant the short body PWK. The internal jetting is easy enough to change.

Yeah, i meant that the needle I got was for a CR500... thats probably why it wont work smile

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9/6/2020 5:49 PM

A good starting point for that application would be an NECW needle in the 2nd clip position ( 2007 Suzuki RM250 needle ) 42 pilot jet / 1.5 air screw / 172 or 175 main jet and your # 6.5 slide.

If that is a little rich at low throttle positions ( 1/4 to 3/8 ) then go to the NECJ.

I'd start with the 175 main. It might be a little rich but it's safer to start on the rich side.

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9/6/2020 10:17 PM

Wangstedt wrote:

Still not getting the bike to run good...

JD jetting red needle taken down 0.1mm or else it wouldnt run at all.
Got the #6.5 slide 45/180 jetting.

Tested the #5 slide aswell but it didnt work, the bike keeps bogging.

Getting kind of tired of this and got no ideas. have like 1 hour on this bike the whole season.


Still no leaks and the exhaustvalve works as it should

digger wrote:

Did you try the needle and specs that I suggested, CCL needle, 48 pilot and 178 main ? They should work with the 6.5 slide best.
What JD jetting kit did you get for your bike ? The small bore JD kit should have needles that have scribe lines under the last clip groove, if not you may have the wrong needle kit.

So i got the CCL and the bike runs good, a little bogging but not at all the same issues as before.

Im running 45/180 because 170 & 175 is to lean on the full throttle.

Thank you so much for the help!

Regards
Christopher

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