2002 KTM 125SX jetting

[chadapotamus]

Hey everyone, I posted this in the tech section also, but didn't know if it would be better posting it in there or in here, so sorry if anybody is reading this twice. I have a 2002 KTM 125SX and am having some trouble getting it jetted correctly. It was jetted pretty much spot on with the stock pipe on it but I just recently put a Doma pipe on it and it's running like crap, I'm not sure what to do. My friend adjusted the needle clip and that seemed to help alittle but it's still not right. It's blubery in some places and screams in others. This is supposed to be a really good pipe, but all I want to do right now is put the stock one back on! Anyone have any suggestions or have any jetting specs that they are running. By the way, I live in So Cal and ride tracks like Glen Helen and Elsinore alot.

 

[bclapham]

chad, i know this sounds daft, but when was the last time you did the top end, they wear quick on a 125 and it will mess withe jetting a lot. (i remember it seemed a bit low on comp.)

maybe one of the guys can suggest which pistons work best in these KTMs

i might be able to ride sunday (work permitting), we can mess wikth it then maybe, lets see about the weather!

also, dont forget to post back with the current jetting specs and which throttle position it is running blurby.

later

 

[chadapotamus]

hey bruce, you may be right about that top end. I was planning on doing one after the Adelanto GP, which next week. The jetting in the bike right now is 48 pilot, R1470D needle, and 185 main. I checked the plug and it is definately rich. I emailed Langston Racing and got a reply back from Gerald Langston, he said the the Doma pipes like to run rich and to start with stock jetting and lean it out one size at a time. The bike feels blurby down low, about 1/4 to 1/2 throttle. I'm guessing that I will mostly need to lean out the pilot jet, but I might have to lean out the main jet also. I'd like to ride sunday if you can. I'll go out and buy pilot and main jets a few sizes leaner and maybe we can mess with it.

 

[bclapham]

you wont believe how much better things run with a new top end!

lets see if one of the KTM experts can suggest which is the best top end to buy, what piston are you currently running?

 

[chadapotamus]

KEIHIN jets

are keihin jets the same for all their carbs, or are they specific from bike to bike. I'm not talking about specific size, but say would the jets from a yamaha work in a KTM if they both have keihin carbs?

 

[chadapotamus]

right now it still has the original piston in it

 

[Studboy]

Most Keihin main jets interchange from what I've seen.

 

[Jaybird]

They are interchangeable, however I have seen jets numbered the same act slightly differently. Used jets can have varnish on them which actually decreases their size.
I use ceramic coated Vertex pistons on my 125sx. Check ring end gap on any new top end.

 

[rm125racer]

Hey chad i also have a 02 sx 125 and ride in socal mainly race town and high desert I just bought the bike from z racing and have left it all stock i am running 100 octane from 76 and run torco gp7 at 40:1 but am getting a lot of oil on the silencer i was wondering what jetting you ran on your bike with the stock exhaust

 

[bclapham]

what is the stock jetting on this bike?

 

[Jaybird]

PWK 39 uses a 190 Main, 48 idle, R1467D middle position, AS 1.5. Mind you this is on a '00 sx125, but I don't think they changed the stock specs.

You should be able to really pep the bike up with correct jetting for your area. Ratio, IMO should be at LEAST 32:1...I run 20-24:1 and have been trying oxy fuel.
I did a little surgery on the plastic around the airbox and gave it a noticible amount of more air. Cut some plastic off and drilled holes. I will try to post pics soon, I think it's a great mod to try.

 

[cp380sx]

I've run into the exact same jetting problems with a 125SX. Get a DDK needle and run it in the 2nd clip position. www.sudco.com has the best rpice. The DDK in the 2nd clip is the same as a 1469H needle in the middle. The 1469H was the best needle for the '01 and '02 125SX. A 48-50 pilot and 190 main should be close as well.

 

[Jaybird]

Too many factors are involved for blanket jetting spec recommendations, unless you write for MXA.
Elevation, temp, relative humidity, type of fuel, ratio, type of riding, etc....what you need to do is have a baseline and understand the changes that take place in each circuit with the changes in conditions.

 

[cp380sx]

Installing a Doma pipe on a 125SX is known to to cause 1/4-mid throttle richness. Installing a leaner DDK needle is also known to solve this problem. I've been through this after installing a Doma.

 

[cappra]

I agree with bclapham it,s probably time for a piston I just changed my son,s for the second time ,(they don,t last for ever ya know!)did you buy the bike the new, it comes with a jet kit and optional needle.
If its any help we are running 02,s at the same elevation ,with the optional needle one clip higher and down one jet size main from stock as well as slightly lower power valve height.