125-200cc i swear my 125 hates me

Installed jd jetting on the mikuni on my 125,

32.5 pilot 430 main jet

Needle ive tried. nearly every position on both needles. Most times ive adjusted a carb in my life.


Idles great, full throttle runs strong.

Mid throttle hesistates and breaks up.

I cant adjust it out with the needles,

Is there a passage in the carb that is possibly related to that throttle range could it be that simple. I cleaned it when started all this.


New plug, clean filter, new top end. Im at a loss.

Try the jetting forum on here, i would suggest a different main jet, breaks up? Revs out or just blubbers? Sounds like too lean so a smaller size main but ive been wrong before and im on lectron now so digging in the memory bank.

Hold it at mid throttle down a long run and check plug .
Is the JD needle designed for older carb ? as it may be differnt to newer style carb.
were you having issues before?
It sounds like how my 09 CR ran and it needed leanest setting on needle - needle at 1 or 2.
Comparison jetting on my older 2008 WR and also using CR ignition - it liked no more than a 400 main and I usually ran it with a 380 main .

"breaking up," is what i use to describe a rich condition. bogging, falling flat, or surging is often used to indicate a lean condition. have you checked to see if the bike has the correct slide? are you able to make the problem worse or better by richening or leaning the needle?

Really lean condition sounds like fire crackerling up top
And the surge at about 30 open throttle boggs then surgers forwards to me is rich.
But that may just be why i bought a lectron

A little background........I was having issues with my 38mmTMX on my YZ 125. My buddy had a Husky WR 125 that was jetted spot on to my YZ carb. So we swapped carbs and the issue was gone. I had a rich issue and could npt figure out the problem. I spend an entire day trying to jet the issue. My buddys carb had been reworked by RB Designs. There was a noticeable difference between his mod carb and my carb.

I sent my carb off to RB Designs for a full mod. I talked to Ron and he said that my carb had gasket leaking?????? I was dumbfounded as to what gasket??? Ron called it "block gasket".......... so when I got the carb back in the box was a funky shaped gasket, along with a bad "o" ring I suspect from the air screw.
I jetted and 420 m 37.5pj and Ron suggested a Suzuki needle which I ordered. The RB Desings carb mod has been talked about on this fourm.

Im suspecting it is something similar.

I ordered a keihn itll be here today, hoping it gets me closer and i can move on with my life hahaha

After trying a lectron to mild success, had g out issues that i wasnt willing to keep fiddling with, after every combo i could try with the mikuni, assortment of pilots mains, needles jd red, blue, white from a yz, stock husky, stock yz, million different combosit would just flat out refuse to run correctly.

Ordered a keihin, installed. Started first kick as delivered, idle was low, adjusted in 3/4 of a turn, runs the best it ever has.

Spent all day on it yesterday 5-7 lap sessions on a sandy, rutted deep track. It did awesome, its a touch rich, but with how hard i ride it in conditions like that rich for me is perfect.

Finally happy.