Kx to KDX???

[Tom Ludolff]

I think my '03 KDX 220 can idle though a whole tank of gas without fouling a plug; but my '01 KX 500 fouls if you putt around too much. Would a flywheel weight make it run smoother and not foul plugs as much??? The plug is always black regardless of how I jet if I don't stay on the gas enough. Why is that???

 

[Kawierider]

Try running a hotter plug, then, try leaning out your pilot get, or increasing your air screw a eight to quarter turn. It is fouling plugs because it is either not running hot enough to burn the fuel completely or, the bike is running rich. These will fix this.
Tim

 

[Tom Ludolff]

Thanks for the response Kawierider. I'm running the pilot 2 steps leaner than stock. I have to have the air screw no more than 1/2 turn out or it starves at idle (surges). The needle clip is in the top notch. The main jet is stock. I was 2 steps leaner than stock, but it died when I'd hit the throttle hard, which made me nervous so I put the stock main back in even though it ran well 1 step leaner than stock. I've tried the 1 step hotter plug also and it still came out black. I just figured then that it just needs to run hard and doesn't like to putt around. I mentioned the flywheel weight because these 2 bikes run very differently. The KDX purrs very smoothly while the KX goes Ring-ta-ting-ta-ting-ting-ting-ta-ting, like it has really high compression or a lopey cam or something. But hang on when you hit the gas!!! Nothing like a KX500 for brute power!!! I would just like to try to make it more woods friendly.

 

[woodsy]

Hey Tom - Your 500 can be cured! It is just not set up properly. when jetting you have to work thru the process in an organized fashion. There are MANY posts/websights explaining how to do ths so I wont go into great detail (do a search) but I will tell you this:
Check your Compression ratio, reeds/pipe for condition, float level and needle/seat, airfilter.
Start jetting by doing a chop at WOT. New plug gets chocolate color!. Do midrange next (mark your throttle with a line drawn on a piece of paper taped to your throttle to show when your at 1/2 throttle) - your needle/orfice may be worn and need replacing! obtain chocolate in mid! Pilot jet size is NOT adjusted by plug chopping. It is adjusted by airscrew count - if "good" idle is obatined by airscrew between 1 an 2 turns pilot is correct!
Sounds to me like your prob is in the float level/mid range needle clip or needle type (they make different taper neeldes too - maybe a straighter taper needle will solve it!)
Do a search - lots of info is waiting for you!
Woodsy
By the way, has your 500 been ported? I have seen this problem MANY times because somebody went crazy with the die grinder! If so - new jug time!

 

[Tom Ludolff]

Woodsy,
No porting. It's bone stock. I bought it new and can't imagine modifying it for more power. It's scary enough already. When I first rode it stock, it would load up on idle and foul when you hit the gas for a second or 2 then clean up. Taking the pilot down a step cured it. It runs perfect, but the plug just doesn't look right. It's always black, but not wet. It starts easily too.

 

[kdxer200]

just ride the kdx

 

[recardie]

Hi
Check if it is not suxing in some air !!

 

[JCW]

I switched from riding KX 250 motocross bikes for the past 10 years to a KDX 200 and I understand your issue. KX's are made to run and run hard. If you are in tight woods, you are probably off of the gas a lot more than you are on the gas. While the bike is awesome for what it is designed for, it's not a real good woods bike unless you can ride like Mike Lafferty or our friend from down under, Mr Watts. Unfortunately, most of us can't handle that pace and that is why I love KDX's. They work for everyone and they still have plenty of power. Most of the KX500 bikes run desert races at high RPM's. While I know you love the bike, I would consider trading it for a second woods bike that fits your style and the terrain that you will be riding. (although I admit that I don't as manly since selling my last KX)
Just a thought-
Have fun
JCW

 

[Tom Ludolff]

JCW, Maybe it is a Manly type issue, I'm not sure. But I do a heck of alot of idling in the woods with it because it is geared so high. That's probably the biggest problem. Only I love to fire across an open field like a maniac sometimes and the KDX just won't do it. I've heard that a flywheel weight will smooth out the rough MX idle and make it more woods friendly. I was thinking if I added the flywheel weight and geared the thing down some it might be better in the woods.

 

[JCW]

I understand 100%. There was nothing like coming out of a turn on a motocross track, hitting the gas and hoping I didn't go off of the back of the bike (I was glad when gripper seats came out). What a rush!!!
I've been trying to give up the MX bikes for years. I think seeing a couple of bad injuries plus my 47th birthday made the call easy for me. While I'm sold on the KDX, there will always be a part of me that wishes I was 30 and still feeling the MX bike "launch" anytime I wanted it to. My KX 250s were all geared too low for the woods. I went from a 13 tooth countersprocket up to a 14 and it really smoothed my bikes out. However, I don't think that would work on your bike. I've heard from a lot of people that the flywheel weights make MX bikes smoother and more like the KDX. I think that is your answer. Have you searched the section Fred refers to in his listing at the top of this page. The answer may be there. Either way, good luck and let us know if you find a way to tame the beast without destroying it's power.

 

[JCW]

One more thing-

Check the "fly wheel weights" thread on page two of this forum. Lots of info-
JCW

 

[Tom Ludolff]

Thanks JCW!!! I'll do that!!!
Tom L.

 

[Tom Ludolff]

I just ordered a Steahly FWW. Raised the forks a couple notches to make it corner better, reduced the compression damping a click, and went down 1 tooth on the front sprocket. I also rigged a tool kit rack on the back so the fender doesn't crack any more from the weight. KX's don't have any frame under the rear fender for support. These bikes have unending low end power with plenty of mid and high also. It should make a decent KDX 500!!! If Kawasaki made a KDX 500, there would be no talk of modifications for more power!!! Like they say, "There's No Replacement for Displacement"!!!

 

[Tom Ludolff]

For all you other Power Junkies out there: One other notable fact is that the KX500 is actually tuned just like a KDX. The rpm:power curve is very linear with no detectable hit like a KX250. Can you imagine if a KX500 was tuned like a KX250 is? It would be totally uncontrollable!!! Therefore, they tune all that extra power to the low end, giving it a smooth linear power curve - just like a KDX, but with massive power!!! The only drawback is the higher gearing, which can be adjusted with sprockets. It will grunt pretty low but a flywheel weight should allow it to run at even lower rpm's for those tight spots.

Anyone have any other suggestions for making this KX500 into a KDX500???

 

[JCW]

Sounds like you are getting it "dialed in". Congratulations-
JW

 

[Tom Ludolff]

Thanks JW!!! All I need is lights and a kickstand!!! Those are the hardest part!!! It would be alot easier if Kawasaki just made a big bore KDX!!! That would be my dream bike!!!

 

[JCW]

I took a standard kickstand and welded it onto the footpeg holder on the left side (like a standard kickstand works). It took a little effort, but it kept me from messing with the swingarm and the frame. It looks like a factory stand that was built for the bike. That may be an option if you don't like the swing arm bolt on MX stands. Check out "Trail Tech" on the web and see if they have a kick stand for your bike. If not, look at their YZ and CR versions for ideas on how to do yours.
JW

 

[Robcolo]

A flywheel weight is not going to prevent you from fouling plugs. Most modern MX & enduro engines are designed with a forward directing "hook" in the transfer ports. This is designed to throw a considerable volume of unburned air/fuel mix directly out through the exhaust port into the expansion chamber. At Higher rpms, this charge comes slamming back in, in effect supercharging the cylinder. At low rpms though the timing is wrong and it is not all burned - thus fouling even a hot plug and You CAN'T jet it out. Eric Gorr has a very simple fix. My Eric Gorr 250 KX idles like a dream, will pull stumps off of idle --and all with no flywheel weight. Simply [well, unfortunately you have to pull the cylinder first] "remove" that transfer port hook by filling it with JB Weld and shaping it to direct the charge straignt across the cylinder. A little side benefit will be at LEAST a 25% increase in gas mileage.

 

[Tom Ludolff]

JCW, Thanks for the kickstand idea!!! I got one from a junk yard, but haven't been able to figure out how to mount it without that little plate that the stand bolts to and the spring hooks on to. I thought I might have to cut one off of a bike at the junk yard, or make one. I might be better of just buying a stand setup and welding it on like you did.

Robcolo, Thanks for the info!!! That's something I would have never thought of in a million years!!! I'll check that out when it's time for top end!!!

Tom L.

 

[dmcc]

Tom, I know you have replied with enthusiasm when I've run a "KDX300" post, and it sounds like you're taking your own route! I am really interested in how it goes. It would be great to make the 500 really woods usable. Some say it feels really heavy. Has this been the case with you?

 

[Tom Ludolff]

Yes. It does have a bulkier feel that I only seem to notice when getting off of my KDX 220 and on to the KX500, even though both bikes weigh about 220lbs. I was just trying to figure out this mystery last night, sitting on one, then the other, then the other, then the other. I think there are 5 main differences that cause this feel: 1) The KX500 gas tank is much wider. 2) The seat is slightly wider. 3) The forks are upside down, putting the large diameter close to your eyes. 4) The forks are longer with a greater rake angle, even when slid all the way up, so you see more fender in front of you. and 5) The 500 has a larger rear wheel. All these factors combined give the feel of a larger bike overall. However, once out on the trail I don't notice it too much.