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Kx125 Jetting Database

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Same as one i just started for the 250 guys and girls


credit for template goes to GMOSS357 from the ktm forums


Model :
Carb size (38 or 36mm): 
Displacement (cc):

Main jet: 
Pilot Jet: 
Air screw (turns out): 
Needle model/Clip position: 
Altitude where you ride: 
Temperature winter/summer:

Head mod:
Other mods:
Type of fuel:
Where in the powerband do you ride (Lugger - for technical stuff, or wide open - desert / MX): 
Degree of satisfaction: 
And finally: how much spooge 1) none, 2) little, 3) medium, 4) lots:


Edited by kxrob

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Year: 2003 KX125

Carb: Stock TMX-38 carb

Slide: Stock slide, no clue what number

Main: 380 in winter, may go 370 in summer

Pilot: 32.5

Air screw: 1.5-2, usually have to adjust during the ride once it warms up

Needle: stock not sure of #, 2nd clip, may use a shim under in winter

Altitude: 7,000 feet

Reeds: Boyesen dual-stage

Pipe: stock expansion pipe with FMF Turbine Core 2 spark arrestor

Head: stock

Other mods: 9oz flywheel weight currently, I usually run without it.

Fuel: 90-91 pump crap

Powerband: All over the place. I ride with newbs a lot and lug it, but live in the high desert so when I get up to my own speed I'm usually in the mid range to high RPM's. I ride singletrack, so high RPM's are usually quick burst only. I also don't let my bike idle for more than about 20 seconds when stopped.

Degree of satisfaction: The bike is running best it ever has, and probably best it possibly can on this carb. Very sensitive to temp change at my altitude. Previously riding in Virginia close to sea level, it didn't seem as temperamental.

SPOOGE: Currently, NONE! Which is a first in the almost 4 years I've owned the bike. I think jetting aside the two most helpful factors for reducing spooge recently for my bike have been to use Maxima Castor 927 oil and a hotter plug (an 8) in winter. I've used Motul 800V(moderate spooge), Maxima super M(horrible spooge), and Repsol off-road(moderate).

Hope this helps someone. I've toyed with the Keihin PWK 36mm idea, but if I can keep it running like it is now when summer comes around, it'll be good enough.

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Bike: 2004 KX 125
Carb size: TMX38x
Displacement (cc): 125

Slide: Stock 5.75
Main jet: 390
Pilot Jet: 32.5
Air screw (turns out): 2
Needle model/Clip position: stock/2
Altitude where you ride: 500ft
Temperature winter/summer: 60-70/80-100*F

Reeds: Boyesen Rad Valve
Pipe/silencer: Pro Circuit Works Pipe + Stainless 304 Shorty
Head mod: Stock
Other mods: No-Toil air filter
Type of fuel: AvGas 100LL 100%

Oil + Mixture: Maxima Super-M @ 32:1
Where in the powerband do you ride: MX (mid to high rpm)
Degree of satisfaction: 8/10
And finally: how much spooge 1) none, 2) little, 3) medium, 4) lots: little/none

Edited by TCMB371

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