[Joeb1983]

Just double checked. It actually has a #180 main and a #50 pilot…

[bo rougeou]

First you need  to look at the literature available on how a PWM  works and the relationships of the needle and jets over  RPM.

And be careful,use only Kehin jets so that the taper fits the needle.

I am no carb expert, but knowing how it should work will point you in the right direction

[Joeb1983]

Yeah, if been reading all about it the past couple days.

Did a compression test and it was good.

Dropped the jets down to Kehin OEM specs. 160 main and a 60 pilot.

This things top end now is a beast and pulls the front wheels off the ground!

Off idle it’s a dog though… Stuttering and bogging. Need to mess with the Air adjustment screw and if that’s not the case start looking into the pilot more.

[Greg Wright]

A check of the needle and needle position may be in order.

[Matt Dixon]

Sounds fat on the pilot.

We have a track that the AA gets over 7000ft. We dont usually get down to a 160, but close, but our pilot is much lower then yours.
But that is with a 99 CR125.

Good Luck

[Joeb1983]

The clip on the needle was in the lowest/richest slot out of the 5.

It’s now in the 3rd/middle and I will just go from there.

I’m not sure why it was setup to run so dang rich…

Maybe it was a carb off something else and he just threw it on to sell it… Who knows?

Learning a lot though! So that’s a plus.

[Joeb1983]

I’m stationed in Oklahoma and our field elevation is roughly 1,200 ft.

Just throwing that out there if that helps. Thanks for the replies!

[Joeb1983]

From all I gathered from the past few days of reading kart & bike forums, articles and sites for both the yz125 and cr125; is I should be in this ballpark:

Main: 170 – 180
Pilot: 40 – 45
Clip: 2nd or 3rd slot
Air screw: 1-1/2 to 2 turns out.

Like Matt said, fat on the pilot with the 60.

I’m throwing in a 170 and 45, 3rd clip, 1-1/2 turns out and see how that goes.

Like I said, the 160 and 60 was just a starting point seeing how that’s what the Keihin PWK 72 came with out the box.

[Matt Dixon]

Fatter pilot to start, those are mighty lean.
If it boggs off corner lean it out, if it hesitates then fatten the pilot.

[Joeb1983]

45 is lean for the pilot?. Most have been 42’s and 45’s I’ve came across for 125’s running Keihins (38 & 39mm)

The richest I’ve seen the main was 185, most were 170 – 180.

It’s apperant I’m confused… haha!

The 60 in it now I know is too rich. Even with the 50 it had in it before seemed a little rich as well.

It doesn’t like to idle and the idle screw seems to do nothing.

It bogs out of a corner for sure. Falls flat on its face… However, up top in the band it rips like I said.

I sent JD jetting an email as well, and I also know every kart/Bike setup is different.

Just trying to get it running right.

It’s been one thing after another and this is the LAST step. Everything else is paractically brand new…

[Matt Dixon]

Remember the 2 jets work together at WOT.

If the 2 motors should be jetted close then try 168/55/dgj2

We ran that just fine with the AA of 2000ft

[bo rougeou]

What Matt said.  Be sure the pilot jet hasn’t picked up any trash.

That will make it behave like you described

[Joeb1983]

The jets in it now are brand new (60 & 160) and I cleaned the carb.

I’m about ready to just order a OEM carb seeing how I know nothing about the history of this one.

Is the PWK 72 39mm to big for a 125? Also, are karts jetted differently than bikes?

Sorry for being a PITA. Just trying to figure this all out… Kinda frustrating. Lol!

All I know is it has a big carb on it, it doesn’t want to idle, the idle screw does nothing, it bogs hard when you first get on it, and it’s a rocket ship up top in the band.

I can bang gears all day long tbat way and it pulls hard. Just that horrible bogging down low when your not ripping it.

101 octane @ 32:1

[Matt Dixon]

We run a 38mm in Stock Moto so 39 will be fine, save your money.

I have told you what you need to do to get it to run, we ran pilots in the 40’s when we ran a restricted Jr125.

It should not idle, the motor fuel requirements are much different then a bike.

Jets are cheap, put them in and you will be close.

New jets get clogged just as old ones do, run a filter.

Trust me go run it and report back, I gave you a fat set up but will “rip” at all rpms.

edit: 32:1 is what we always run

[Joeb1983]

I really do appreciate it. I’ll head to the shop and grab the jets you recommended or order them if they don’t and a few other close in that range.

Thanks again. I’ll let you know how she runs. I’ll run through the carb again as well.

I should stay with the 3rd clip setting right?

I installed a new pump, lines and filter as well last week.

[Joeb1983]

Update: ordered a JD kit. ended up installing a 55 pilot, 175 main, blue needle with the clip in the 3rd notch. Air screw 1-1/2 out.

(Kit didn’t have a 168 main, but came with a 162,170, 175 & 180)

17O was a little lean up top my buddy said according to the plug and 180 was a little rich.

She idles now and the idle screw actually works!

Low end cleared up nicely. No more bogging/hesitation. It’s now acting like a typical light switch 2-stroke. Lol!

Plugs is a light tan color after a WOT pull.

Thanks again for all the help guys!

[Author]

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