2004 cr125 tips

Dillpickle312
Edited Date/Time 3/31/2020 11:58pm
Hey guys I’m rebuilding my 2004 cr125 and I know this is the red headed stepchild for cr125s but i know there’s some minor hop ups available for it. I have vforce reeds already on it. I’d like a pipe but that’ll have to wait for now. Iv heard of switching the airboot/air box to a 2007 airboot/box do I have to get just the boot or the whole air box for that? I’d also love to get a 38mm pwk for it as I heard that’s great for it to. I’d like to keep the engine mostly stock as this is not going to be an all out race bike that I need all hp I can get. Thanks in advance!
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KX500
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KX500 3/26/2020 7:39am
3/26/2020 7:39am
I installed a Keihin Airstriker on a 2002 CR250 not that long ago. It was a huge improvement. Went from a bike that would foul a plug in a heart beat to total reliability.

Swap was easy. Then sold the old TMX on eBay. Swap was super cheap that way.

The hardest part was the air box boot. The boot from the '02 was too short to begin with and was almost impossible to get back onto the carb. So I bought a boot from a newer model CR250 - '04-'05 maybe. Much improved boot, it simply had more material and was pretty easy to get over the carb. I bought the boot only, and swapped it out with the original one on the '02 airbox.

Then sold the old one on eBay. Swap was super cheap that way (might be a trend there!).

Anyway, not sure what years CR250 and CR125 shared airboxes and maybe carb boots, but maybe a little research can reveal that too.
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seth505
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seth505 3/26/2020 8:13am
3/26/2020 8:13am
You just need the newer boot, not the whole air box. I had an 03 I redid and it ran super crisp with the stock TMX. I'm restoring an 05 right now. Have fun
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seth505
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seth505 3/26/2020 8:16am
3/26/2020 8:16am
I did a little air box venting to help feed it more air as well.


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Dillpickle312 3/26/2020 11:49am
3/26/2020 11:49am
seth505 wrote:
You just need the newer boot, not the whole air box. I had an 03 I redid and it ran super crisp with the stock TMX...
You just need the newer boot, not the whole air box. I had an 03 I redid and it ran super crisp with the stock TMX. I'm restoring an 05 right now. Have fun
Awesome thank you

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digger
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digger 3/26/2020 1:28pm
3/26/2020 1:28pm
Like has been mentioned above, you will only need the air boot from an 05'-07'. In 04', (04'--07') Honda switched to a TMX-x carb which is 75mm in length vs the older TMX carb, which is 91mm. If you do go for a Keihin PWK carb, you will want to get the later, 75mm, version. The older, screw on top pwk, is 91mm in length, and makes for a tight fit.
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JOE_SPROCKETS#1 3/27/2020 6:11am
3/27/2020 6:11am
seth505 wrote:
I did a little air box venting to help feed it more air as well. [img]https://p.vitalmx.com/photos/forums/2020/03/26/413449/s1200_IMG_7716.jpg[/img]
I did a little air box venting to help feed it more air as well.


Did this modification help any? Could you tell a difference? Might do it to my cr 125
seth505
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seth505 3/27/2020 9:47am
3/27/2020 9:47am
JOE_SPROCKETS#1 wrote:
Did this modification help any? Could you tell a difference? Might do it to my cr 125
Unfortunately, I cannot answer that. I bought the bike from a friend who sent the motor to multiple shops and never was able to resolve a huge bog/water in the engine issue. I tore it down to the frame and built it up exactly how I wanted and got it running pretty damn awesome. I did the vents on each side of the air box just to help encourage as much air as possible. I'm building up an 05 right now and I'm going to put in the same vents.
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Dillpickle312 3/27/2020 10:05am
3/27/2020 10:05am
Also for my 38mm pwk will I have to rejet it to go on this 125? Or should it be ready with stock jets?
digger
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digger 3/27/2020 10:11am
3/27/2020 10:11am
What bike did the used pwk come from ? It will for sure need to be rejetted.
Dillpickle312 3/27/2020 10:48am
3/27/2020 10:48am
digger wrote:
What bike did the used pwk come from ? It will for sure need to be rejetted.
2000 cr250
digger
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digger 3/27/2020 12:47pm
3/27/2020 12:47pm Edited Date/Time 3/27/2020 4:22pm
digger wrote:
What bike did the used pwk come from ? It will for sure need to be rejetted.
Dillpickle312 wrote:
2000 cr250
That bike used an AS1 PWK, which is a long body,91mm, carb. The fit is going to be a little tight with the 05-07 air boot, but it will work fine. To get you in the ball park jetting wise, I would use a single taper CCL needle,and start out in the 3rd clip position. The pilot is gone to be around a 50 or 52, depending on the air screw position, and I would start out with a 185 main to stay on the safe side, and go down from there. Set the air screw a 2 turns out, and adj as needed. This is all assuming that the carb has the original #7 slide.

https://www.jetsrus.com/individual_parts/017_464_su.html
Dillpickle312 3/27/2020 1:19pm
3/27/2020 1:19pm
digger wrote:
What bike did the used pwk come from ? It will for sure need to be rejetted.
Dillpickle312 wrote:
2000 cr250
digger wrote:
That bike used an AS1 PWK, which is a long body,91mm, carb. The fit is going to be a little tight with the 05-07 air boot...
That bike used an AS1 PWK, which is a long body,91mm, carb. The fit is going to be a little tight with the 05-07 air boot, but it will work fine. To get you in the ball park jetting wise, I would use a single taper CCL needle,and start out in the 3rd clip position. The pilot is gone to be around a 50 or 52, depending on the air screw position, and I would start out with a 185 main to stay on the safe side, and go down from there. Set the air screw a 2 turns out, and adj as needed. This is all assuming that the carb has the original #7 slide.

https://www.jetsrus.com/individual_parts/017_464_su.html
Aweosme thank you! Needle ordered!
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Tracktor
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Tracktor 3/31/2020 11:19am
3/31/2020 11:19am
Spend a bit more and put a STIC metering block in that PWK. You seriously won't regret it. I feel kinda like a shill for these but the difference is hard to describe until you ride with one-250f power curve out of a 125.......

http://www.sticsupertorque.com/

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