Smoking KDX 250

[Hawk5443]

Hey guys--I just joined and wanted to get some feedback on an issue that has been frustrating me. A couple of months ago I purchased a '92 KDX 250. It runs great--plenty of power, but smokes and blows a lot of oil. I am running 50:1 Belray, so I don't think that the mixture is too rich and there is no loss of power that I can tell. The compression is up around 150 psi, so I doubt that it needs a top end. I took it to the Kawasaki dealer and they said not to worry about it and just ride it. If it keeps smoking and blowing oil like it is, I will be changing the packing and de-greasing this thing after every ride. Does this sound like a jetting issue? Any help would be greatly appreciated. Thanks.

 

[dirt bike dave]

If your jetting is stock, it is almost certainly a jetting issue. The stock jetting on the KDX250 is way too rich.

Most owners will drop several sizes on the main jet as well as the pilot jet, and put in a leaner needle. And if you really want to optimize the jetting, you will go for a slide with more cutaway (or modify your stock slide).

I had a '91, and there is a lot you can do to improve the bike. One of the members, 43duc748, has assembled much of useful set up tips into a webpage. Here is his link http://www.garage.whatburns.com/KDX2.htm

 

[Hawk5443]

Smoking KDX

Thanks Dave. I will look into making those mods. A friend thinks that I may have a scored spot on the low end of my cylinder and that it may be pulling a little crankcase oil up and burning that, thus creating the excess smoke. Does that sound like a possibility?

 

[joebiodiesel]

Thanks Dave. I will look into making those mods. A friend thinks that I may have a scored spot on the low end of my cylinder and that it may be pulling a little crankcase oil up and burning that, thus creating the excess smoke. Does that sound like a possibility?

Hi Hawk,
No, not possible, It's a 2 stroke. There is no crankcase oil.
As others have advised, get the jetting right. Once that's in line, you can rest assured that whatever smoke it's making is normal.
Joe

 

[Hawk5443]

Smoking KDX

Joe,

Thanks for the confirmation on that. I meant to say gearbox instead of crankcase. Hopefully, I will have some time to work on leaning it out this weekend. For starters, I am going to pull the snorkel out of the airbox and possibly change the clip position on the needle to try to lean it out some. If that does not do the trick, I will spring for new jets.

Thanks again.

Tom

 

[Hawk5443]

Smoking KDX

What would be your suggestion on jetting for sea level up to about 1500 feet?

 

[dirt bike dave]

Using premium fuel from the pump, I would start with a 160 main (your stock is 165, I think), a 38 pilot, the R1367H needle 3rd clip from top.

You might find the 158 main works better, so I'd buy one of those and experiment.

FWIW, I had a 155 main in mine on a dual sport run down to sea level, and it did ping a little on the highway when accellerating in top gear, so I think the 155 will be too lean for your elevation.

 

[KdX_SkUiRrEl]

Did you forget your riding a two-stroke? a '92 Kdx at that? it doesnt matter how perfect you get thte jetting, its still going to smoke and spit oil. If your really worried about jetting, go 5% smaller from stock on both pilot, and main jet sizes, and you should be in the ball park. I had my '95 kdixxer in my shop when we were slow, and did the jetting. Its pretty much perfect, but It still smokes, and spits oil :bang: . Its ineveitable. But im just a motorcycle mechanic, what do we know :) :coocoo:

 

[antonyp]

Did you forget your riding a two-stroke? a '92 Kdx at that? it doesnt matter how perfect you get thte jetting, its still going to smoke and spit oil.

I second that :cool:

But I still love my KDX to bits even though I need to change clothes after every ride LOL :ride:

 

[maxellfullmoon]

Crankcase seals

Crank seal may be worn out and letting the tranny oil enter the crankcase. If you keep running it just keep a check on the tranny oil to see if it's loosing any. This happened to my KX500. I left the gas on for a few months, the float stuck and filled the cylinder with gas and ate away the seal.

 

[dirt bike dave]

Yep, it will still smoke and drool some oil with the leaner jetting. That's the nature of a two stroke trail bike where you are idling or at part throttle much of the time and using pump fuel. But it will smoke and drool a lot less than his bike did with stock jetting.

With the leaner jetting, it will also run stronger and foul fewer plugs.

The stock jetting on the '91 - '94 US spec KDX 250 is way off, even for sea level. No reason to live with jetting that bad.

 

[Hawk5443]

Smoking KDX

Well, I got into it this weekend and found that the prior owner had replaced the main with a 158, which is two sizes down from 160 that I planned on putting in. I dropped the needle all the way down and rode it a bit. It could need a ring job, or I could just be bitching about something that it is always going to do--smoke and spit oil. I will probably just shut up and ride it. My transmission oil level remains constant and it does not smell like anything other than 2 stroke oil. Thanks for everybody's imput.

Tom

 

[antonyp]

I will probably just shut up and ride it.

I have been doing that for the last few years myself. The bike still smokes a lot when cold (not so much when it's warmed up) and drools like a baby on a pram, but as long as I stay at sea level it runs great ! :ride:

Thumbs up for the KDX :cool:

 

[Hawk38]

+1 I just joined and this was exactly the info I was looking for, thanks guys. I have a '96 that I haven't ridden since before I left for college. I had a few bad wrecks, then I went off Mom & Dad's insurance so it was garaged for.....7 years...wow, thats depressing. But a quick carb clean and it fired up on the second kick, just like the old days. Now that I have the means, I am going to tune this thing with some quality aftermarket parts and this was my first concern. Anyways, thanks for the info and sorry for the thread hijack.

 

[antonyp]

Always a pleasure to see a fellow KDXer up and running again :) :ride: :)

 

[cruel2bu]

I have played with my 1994 KDX250 for about 7 years now and it spits and drools oil.I have done different jets and tuning on it and it cleaned it up alot but it still is not as clean as my 2004 kx250.But alot of it is from idling and low speed running then when you open it up it tends to clean the pipe out and spray it all over the person behind you if they get too close. :)

 

[antonyp]

...it tends to clean the pipe out and spray it all over the person behind you if they get too close. :)

LOL :laugh:
I wonder how far it will spit that oil if I straighten the endpipe of the silencer so it looks straight back instead of an angle :laugh: :laugh:

 

[2strokerfun]

One thing I learned the hard way is that a worn jet needle or slide (usually needle) can cause excessive smoking no matter how you jet it. And yes they smoke, but when set up right, it isn't excessive or annoying.

 

[kid1293]

right on the money cruel2bu i have a 90 for about 4 years and it smokes on warm up but once it is hot and pipe cleared out it is just a reg. 2 stroke and thanks for the deleted reply the other night dave. :p