Jon Mitchell

I am researching how to tune a 2002 Suzuki RM125. I have read of controls with different names and my guess is idle adjustment screw and air screw are the right terms for two different controls. Can anyone tell me if my carburetor has both and if so, which is which.

Here is a photo of the Mikuni carb on my son's bike:
Mikuni Carb

The red arrow points to the one screw I can find that I assume does something. My guess is this is the air screw. Yes?

So do I have an idle adjustment and if so, where is it?

Thanks in advance.

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2006 Honda CRF 250X

tigmaster

You don't have an idle screw. Your carb relies on sketch and science aka FM to idle properly. That should be your air screw. I could be completely wrong but that is how almost all the 125cc two stroke bikes do it.

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gscx

that is the idle screw, my Yz had it there. The air screw is pretty well hidden, its on the end that is closest to the air box, like on the bottom on the opening, it might have dirt blocking it so look real good

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199? KX60- Bone stock and in process of complete rebuild and restoration

turtlemann14

i find the air screw in on the right (as you are sitting on the bike) on most carbs

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tigmaster

CR125R's do not have an idle screw. I have also seen it on some years of RM125's which is why I assumed his was the same. They should all share the same carbs during the same general period.

I would have to see the carb to fully answer the question. A quick look inside tells all.

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gscx

here we go.
2002 Suzuki Motorcycle Parts for RM125K2, OEM and Aftermarket at BikeBandit.com

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199? KX60- Bone stock and in process of complete rebuild and restoration

Jon Mitchell

Found the air screw. Little tiny thing way down low and somewhat hidden. The diagram really helped...after staring at it for 10 minutes. Thanks everyone.

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2006 Honda CRF 250X

doomed

thats actuallu a throttle stop screw wich should be turned in just till it starts to lift the slide the idle is adjusted by turning the choke look at the top of the choke im sure it will have directional arrows there and you will want to find the stock setting for your air screw most of them is 2 1/2 turns i think wich will get the bike to start then you adjust it back and forth untill you find the point where it idles the highest and then if the idle is to high you adjust your idle screw out until its where you want it

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doomed

now i could be wrong on that idle screw being the choke i just remebered my rm had a keiin on it and your is a mikuni so im sure they are differant

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Jon Mitchell

Can I resurrect this thread or should I start a new one.

Since rejetting the bike...and then rebuilding the engine, I find that I need to adjust the idle. After warming up, the bike is idling fast. It doesn't decelerate that well and it pushes you around corners unless you slip the clutch.

I have determined that I have a throttle stop screw (the one in the picture I posted) and an air screw (the one gcsx helped me find). I have never got around to messing with them and its too damn cold out tonight to try, so I thought I'd ask... which one should I use to adjust idle.

After reading the service manual section on carberator adjustment I'm still a bit confused, so correct me if I'm wrong. Looks like I use the throttle stop screw to adjust the idle. The air screw is to adjust air flow for up to 1/4 throttle and works with the pilot screw. ???

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2006 Honda CRF 250X