New KDX owner-jetting & oil/gas ratio


Mar 26, 2008
I've always ridden 4T's, still do (XR's) As a recent 2T (95 KDX 200, heard great things about them) owner I find several things about them a little more complex than 4T's. I'm not ragging on two-strokes I'm just learning about them so, no "flames" are called for. :nod:
The oil/gas ratio is one. (Riding technique too, but that's another thread.)This ratio is one extra element I haven't had to deal with. I read a lot on all the off road sites re: jetting and gas/oil mix. Settled on 50:1 and 45/155 1173 jets, FMF Woods pipe, Boyeson reeds, airbox open,runs best w/air screw at 2 turns out. Bike starts, idles and runs fine (good "hit") from sea level until I get to slightly high altitude ('3000) then runs real fat and has a loss of power. (The 4T didn't notice this altitude.) Tried adjusting the air mix screw briefly, didn't notice a change. Hmmmm. I noticed there is just a slight amount of "spooge", like just a drop hanging from the pipe and slight smoke after it warms up. Plug looks OK, tannish.
There are a lot of opinions on oil/gas mixture. I really didn't feel comfortable with 50:1 Golden Spectro, so I think I will go with 40:1 Amsoil. Nothing against Spectro, just heard good things about Amsoil. That will lean my mixture a little bit. Perhaps enough where 1) I won't have to rejet? OR...2) Is this normal for 2T's to run noticeably richer at '3000? 3) Could I have another problem? (Low speed and main jets are both new, carb is clean and filter is oiled.)
Those are my 3 questions.

Now, observations and musings. :blah:

With a 4T, when you open the airbox and change exhaust you know that leans the air/gas mix so you fatten up the mixture and jets. That's it.
With this KDX 2T, recommendations are to 1)lean the jets because they are too rich stock, 2)open airbox lid which leans it even more and 3)new pipe which leans it more then 4)change the oil/gas mixture to 50:1 which richens :yikes: it up to....? somewhere. Hard to know where you stand. Just have to ride, adjust, ride adjust I guess. I'm OK with that. I enjoy it.
I'm sorta thinking out loud and here, sorry for the rambling.
I love the lightness of the KDX (25 or so lbs less than the 250)
and the "hit" of the power valves. I really like the KDX now, and when I get it sorted out, and learn to control the power and going downhill with no engine braking, it will be great.Two strokes are a new world for me. Maybe I just have to learn to be less simple and more comlpex!!!??? Smarter??? :)


Jan 25, 2003
I've been using Golden Spectro at 64:1 since my first KDX in 1981. Haven't had a problen yet (2oz. for each gallon of fuel). Any more and I get splooge. Golden Spectro is a concentrate....ya need less to get the job done. Cheers.

John Harris

Apr 15, 2002
Based on my experience, you will enjoy a 42 pilot jet. With that pilot, you should not notice a problem at 3000 feet. Maybe beginning at 5000. Power does go down with an increase in altitude. Be sure your air cleaner is in good shape at altitudes. Settle on an oil and a ratio and then resolve your jetting. Ride safe John
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