03 kx125 jetting/plug

[PDW]

i have done the necessary searches and found some good info but i just want to know that if im fouling plugs, leaking spooge like crazy, and there is a slight burp when i crack the throttle what jet should i be changing first. right now its stock with the clip raised to 2nd position main-420, pilot-40, with a vforce 2 installed running pump 92 and klotz r50 at 32:1

i have seen the other threads suggesting a 400 main and 35 pilot. should i just change them both? i was thinking going to a 400 main and 37.5 pilot to start. any better advice out there ?

ALSO- i refuse to run the br9eix plugs due to MANY MANY people expressing breakage issues. i dont want to run the expensive rm plugs either. is a br8eg too hot for my bike? should i go br9eg ? any help is greatly appreciated

i should have also mentioned that i do have a copy of that good jetting guide but i am entirely new to jetting so i need to be absolutely sure before i dive in..

 

[kxmike]

on my 2003 kx125 i have the vforce2 and a pc pipe and silencer and i went to a 37.5 pilot but its still a little rich so i might go with a 35 and i have the stock 420 main in there. honestley i have never had a br9eix plug break or anything and ive been using these plugs since ive got the bike because the br9eg i used and it didnt last long at all and made the bike act like it needed to be cleared out. i ride in the powerband so i know it wasnt me or my jetting it was the cheap br9eg plug i got. i am kinda scared going to a 400 main jet it seems kind of lean but i am going to order a whole bunch of jets and just try them out.

 

[holeshot]

I've gone to 27.5 pilot on mine. Work your way down gradually with pilot size until the spooging stops.

Careful with the main jet - going too lean could cause trouble...

 

[Ryan31783]

I'm at 5700 feet of elevation, I tried a 32.5 and it was too lean (BWAAHHHH when opening the throttle at about 1/8 throttle) Put in a 35 with 2.5 turns out and it's just great ... Needle is on the 1st position, 380 main, and I'm also running a BR9ES plug, runs great.

 

[LA Sledboy]

Ive got a 02 125 w/ fmf pipe and silencer. stock pilot and clip position but I think it was a 350 main in when I got it. Anyway Im running 300 main right now. Lean and mean. Still having low end problems. Is there a fuel/screw on these carbs or am I missing something? Im a sledhead so bikes are kind of new to me. Oh and before you say 300 WOW!! I ride it up to 10000'

 

[LA Sledboy]

Actually it might have been a 400 cant remember. Anyway like I said Im a sled head but its all the same. I was looking over my carb and didnt see the usual air/fuel screws Im used to. Figured it out though the idle screw is the one with the locknut which Ill be having to change since it wont idle then Ill turn the air screw out 1-2 turns and see how she livens up. Not that the performance is too poor at the moment. Im also going to drop the needle a clip or two (probably two). Asking for trouble eh? :D Oh also Im thinking about running a br8 or br7 instead of the br9. Like I said before guys Im at 8000' where I start and its up from there.

Even though this is a MX bike its not WOT all the time or much at all. The throttle is probably in the middle the most and I am a clutching fool on these high rocky rutty mountain trails. Great place to learn how to really ride one of these bikes though right ;)

 

[pw50123]

I am @ 700 ft in Michigan. I went down to a 410 main and a 35 pilot. I have stock reeds and a DEP pipe and silencer. This does no bog or spooge anymore and the plug looks great. Once you get your jetting set you can afford the expensive plugs again and change it twice a year!
Hope it helps.

Also the DEP pipe and Silencer work great. What a diffrence. I found them on E-gay $125.00 for both!

 

[PDW]

ya i read on the "bolt-on bonanza" article of a mag that those were a good choice of aftermarket exhaust for the 03 kx...good to hear some real feedback tho
btw where in michigan are you from? i am sometimes in the u.p and i live down near windsor

 

[djp2k3]

I have an 03 kx125 with fmf pipe and v-force 2 reed cage. Before the v-force I was running 410 main, 37.5 pilot, needle 2nd clip. After the v-force I dropped to a 400 main, 35 pilot, and needle 1st clip. It's still a little rich in the needle, though. This is a tough bike to jet.

 

[marcusgunby]

Its the pilot i went down to a 30 on a friends, airscrew at 1 turn.