02 CR125 Flat Spot

I posted this problem in Honda 2-Stroke but maybe someone here can help...

I just picked up an 02 CR 125 and noticed it had a flat spot in it. You have great response from closed to 1/4 throttle. You go from 1/4 to 1/2 or 3/4 and there is a flat spot that you have to feather the throttle to get through it. Once you get through it, it will put you in the power band and pull hard. My question is how do I fix it.

So far I have taken the carb off and made sure it wa clean. Also I saw that the jets were not the correct ones. I have a Pro-Circuit Works headpipe and Pro-Circuit R304 Shorty silencer on it. It had #410 main, 35 pilot and needle clip in the middle. On Pro-Circuit's website it says it should have #390 main, 32.5 pilot, and needle clip in the middle, air screw 2 turns out. I changed the jest to Pro-Circuits specs. Also it has a new top end and new Boysen Reeds. I also tried changing the needle clip up and down and putting it in the second notch (richer) it runs a touch better than the middle but not alot, still have a flat spot. Next I am gonna check to see if I have an air leak around the reed valve. Is there anything else I can check or try to do to get rid of that flat spot? Should I mess with the air screw some more and try that? If anyone has any ideas please let me know. Also I am at an alttitude of around 2000ft. Also my needle jet is 6DFY5-74. On Pro-Circuit it calls for a 6DFY-74, are these needles the same ones? Thanks in advance to anyone with some answers.

Also I assume the original owner used 32:1 pre-mix. I know he used Castor 927, just not sure on mixture. If anyone thinks of anything that could help, thanks in advance.

Sounds lean on the needle taper, try raising the needle by lowering the clip position. 1 being the first position near the end of the needle, 5 being the last position. You said it was in the middle position so raise it to the last (5th position) and see if it is better. What you have done is pull the needle out as much as possible, thus making it richer in the 1/4-3/4 area.

If it is better but not quite there, you will need to get a richer needle, in the taper.


Ok right now I have the clip in the 2nd notch which is richen it up and it was better and my next move was to move it to the 1st. Do you know what the number of that needle would be? Or could I look it op under oem Honda and look for a richer one? Thanks Dave.

Do you know what the number of that needle would be? Or could I look it op under oem Honda and look for a richer one? Thanks Dave.

Get the number from the needle and go and see your dealer and ask for the next step richer.

put that needle in the midle clip and test again, fine tune by going up or down on the clip position until it runs sweet.


Will do thanks Dave. I am gonna try one more notch on my factory needle I have now then if it isnt better then I will go get a richer one. Just looking for a smooth transaction is all.

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