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Craig’s KDX Page

This page is devoted to technical notes about the Kawasaki KDX, especially those affecting my old bike, a '91 KDX200F (aka "SR").

First, some external links

KDX fans should visit Canadian Dave's JustKDX site and its discussion forum for great technical and other info on the KDX series.
See also the forums at
A handy fuel-oil ratio chart (PDF format).
How to read spark plugs.
Two-stroke enthusiasts will find some interesting links on this page and this one.
Also see Eric Gorr's site for great discussions on two stroke engine issues. Check out the article entitled Two-Stroke Top End & Powervalve Tips for example.
A nice illustrated tutorial on later-model KIPS powervalve work.
A whole bunch of great info on KDX SR model.

How to convert the KDX for motocross use.
A workshop manual for the 1989-94 model KDX200.

KDX-related links of mine

Powervalve modification for earlier KIPS systems.
240 big bore kit notes.
Album page and pics of my bike
My assortment of parts fiche schematics collected from BikeBandit (more available there)

240cc big bore sleeve
My 240cc big bore sleeve as seen from below (bored to first oversize)


Odd KDX notes

Kickstarter fails to engage
If your KDX kickstarter is difficult to use, slipping past the ratchet mechanism and slamming into the footpeg instead of spinning the motor over, it's because your oil is too thick. KDX kickstarters are sensitive to gearbox oil weight for some reason, and you will notice that the problem is worst when the oil is cold and thickest. I have found that 20W-50 causes this problem on my bike.
You can either put up with it, gingerly finding engagement before swinging, or switch to a lighter viscosity oil. Automatic Tranmission Fluid of the Ford (or "F") type is also ideal for two-stroke gearboxes as it's designed to cope with severe forces generated by gear sets and wet clutches. It works well for me. See this thread.
Whatever you do, don't choose an automotive oil that contains friction modifiers. These will cause the clutch to slip and burn out. Many premium car oils contain friction modifiers these days. Be careful.

Gearbox oil milky grey colour
If your gearbox oil has suddenly turned milky, it's probably because you've got water in it. This water could have come from two places: the cooling system or the outside world. If it's coolant in the oil, you have a bad water pump seal. If it's from the outside world, you have probably been stuck in a puddle or river recently.
Water is drawn in through the gearbox breather tube, which hangs down and begs for water to enter. If the bike spends long enough partially submerged in a cold puddle or stream, the hot air in the gearbox will be chilled, causing it to contract. This will create a vacuum that will suck in whatever is at the end of the breather tube—-in this case, water. It happened to me in a big muddy puddle that turned out to be deeper than it looked.
I suggest modifying the breather tube so that its outlet is higher up on the bike. I've re-positioned mine and intend to arrange it later so that it opens into the airbox.
In the meantime, drain the watery oil. I flushed my gearbox through with diesel fuel mixed with a little engine degreaser from a spray can (detergent is useful to pick up the water), then replaced the oil with cheap stuff and drained this again after one ride. This ensured that all the water was removed.
Note: I have read about one obscure brand of oil that goes milky on its own without any water being present, so switch brands if in doubt. Also, don't confuse milkiness in the oil with the silvery sheen that clutch particles produce.

Gear lever floppy
If your gear lever suddenly goes limp or floppy and you have trouble changing gears, it's probably a broken spring. You don't need to pull the crankcases apart, just remove the clutch cover on the right side of the bike. Pull the clutch off and you should see whatever remains of the spring sitting there, perhaps with one of its two extended arms broken off and floating around below. It's an inexpensive part that can fracture on very rare occasions (mine did).
If you have trouble getting the clutch nut off because it's tight and the clutch plates slip, try jamming a piece of steel pipe through the rear sprocket so that as you turn the clutch the pipe binds against the swingarm. Put the bike in a high gear if you can (to reduce the mechanical advantage). It's best to use a piece of pipe that will go right through the wheel and over the top of the swingarm's right side too. Be careful to select an opening in the spokes that will keep the pipe away from them so that they don't take the strain. Then have another go at the clutch nut. It's a normal right-hand thread, so turn it counter-clockwise. The pipe should lock everything up nicely and allow you to undo the clutch.
Use the same technique to tighten the nut later, but Locktite on the thread is the best insurance.
By the way, if you ever get stuck out in the bush with this floppy lever scenario, you might find that you can still change gears with the correct foot technique. I found that I could use the side of my boot to sort of wiggle the lever between gears. It saved the day. This is much better than being stuck in a high gear and burning out the clutch while trying to get home.

Coolant overflow tank always empty
The plastic coolant overflow tank under the left sidecover on pre-'95 watercooled bikes will tend to lose its fluid no matter how often you top it up. Why this happens is a bit of a mystery. Some say that it gets sloshed out the small overflow tube. Personally I have wondered if it sort of just gradually vapourises off because of the incredible aeration and agitation that it gets from engine vibes and all the violent heaving around when riding. Don't fight this problem in vain, just run the overflow tank empty and keep an eye on the radiator level, which will stay pretty constant without the benefit of any overflow reservoir fluid.
Some KDX owners remove the overflow tank, but it doesn't hurt to leave it in place to catch and condense any vapour and allow the radiator to suck it back in again later.
Enlarge Update 7/03: I recently followed a suggestion posted by someone on the KDX forum and bent the overflow tank outlet nozzle upwards slightly to prevent liquid sloshing out. It worked! I was amazed to find the overflow tank full after a very rough day's ride. This is the first time it has retained its fluid. Here's what to do: If you remove your left sidecover and seat, you'll notice that the overflow tank's outlet or breather tube is positioned at the top and sits horizontally. You need to bend this upwards at an angle so that any liquid that slops into it runs back down to the tank. I used an electric heat gun on the plastic tank at the nozzle junction. The heat softens things enough to let you bend the nozzle upwards. Be careful not to pinch off the inside diameter. You have to clear the subframe tubes somehow too. I elected to point the nozzle outwards as well as upwards, and re-route my breather tube so that it now runs around the outside of the frame (see pic). This seems to work fine and just clears the seat and sidecover. That's it.
See this thread for more. To reportedly cure boilover once and for all, use the (expensive) waterless coolant made by Evans Cooling.

Countershaft seal leaks
Enlarge The KDX countershaft seal can leak gearbox fluid. Apparently, it's caused by using aftermarket sprockets which are often different widths to the stock item. These can fail to apply sufficient pressure to the o-rings to keep the fluid in, or something. Using two o-rings seems strange, but I've heard that you can adjust the number to suit the width of the sprocket.
Of course, many leaks are the result of ordinary wear too, which can be severe at such a muddy point on the bike. My countershaft seal was definitely worn badly, as was the steel sleeve it rides upon. To save a few bucks on the seal, avoid buying a Kawasaki item. Go to a bearing specialist and ask for a seal with an inside diameter (ID) of 30mm, an outside diameter (OD) of 40mm, and a thickness of 7mm. The o-rings are just thin 30mm items, which you can possibly buy at the same place. To pull out the old seal without disassembling the engine, just make a notched extractor tool out of, say, 6mm or 1/4-inch rod. With the sleeve removed it's easy to slip the rod in and pull the seal out (Crows in New Caledonia make similar tools for extracting grubs from logs, which says a lot for the intelligence of crows, and a bit less for ours).
If fixing all of the above doesn't cure your leak, a friend said he has had success on some bikes with shoving silicone in behind the sleeve. Why not!

Oil Injector needs adjusting (international SR models)
The following procedure applies only to SR models that use a separate oil tank and injector system (those that don't use premix fuel). This info is kindly provided by Tico in Costa Rica:

First, make sure your throttle cable is properly adjusted—nice chance to oil it.
Oil pump adjustment is as follows:
1. Remove the carb.
2. Remove the lid that is behind the carb (it's only two screws).
3. Check the adjustment by moving the throttle cable from idle to WOT (wide open throttle). Note there are two marks: one for idle and other one for WOT.
4. Adjust as necesary (top right adjustment screw). Mine was was way open. I closed it until it was just a bit after the mark (1 mm to give some extra protection).

Well, that's it. Pretty straight forward, all you need to know is where to locate the adjustment and marks.

Fork Oil Specs (for bikes similar to mine)
Stock spring preload spacer is 110mm (my bike has two extra PVC spacers per leg, totalling 47mm on top of the 110 standard spacer - felt good for my 90kg).
Jeff Fredette suggests (referring to 1990 model specifically): 7.5 wt oil, 4 inches (102mm) from top of the leg. The Kawasaki manual apparently specifies 140 mm +/-2mm.
I have scribbled down these volumes from somewhere: 618 ml per leg (range, 614-625ml).
Note: Oil level is measured with the springs removed and the forks fully compressed. 7.5wt oil can be made with a 50/50 blend of 5wt and 10wt. If you can buy 7 wt, that's close enough. I used 5 wt plus a dash of 20 wt, which I had on hand, 100mm from top, and it worked beautifully. If you can't get fork oil, some people use automatic transmission fluid instead.

Big End Specs (probably applies to all KDX 200s)
Con rod twist 0.03mm /100mm
Big end radial clearance 0.020-0.043mm up & down play
Side clearance 0.4-0.5mm
Crankshaft runout under 0.03mm
Thanks to Dogz in Ontario for the above

Following are some general notes about my 1991 KDX200SR

Go to my album's KDX 200 pageMy jetting might interest others working on a similar setup. I had the 28mm PE carby that came standard on this bike. Enduro models have the 35mm PWK carby. I was intending to upgrade, but realised after a while that the smaller carb is ideal for the tight, steep, slippery tracks that I rode, allowing finer throttle control, better bottom-end torque, and overall faster riding. Top-end power is still way more than I could use in these circumstances 95% of the time.

  • Main Jet: 180 (probably a bit rich, but not by much).
  • Needle: Stock N68K needle. Currently has the straight section built up with silver bearing solder to lean off the low-end. This was only intended to be an experiment, but it works very well and has greatly helped low-end richness and poor idle. Never got around to replacing with the right Keihin needle.
  • Needle Clip Position: Top notch, but might be compensating for too large a main jet somewhat.
  • Pilot Jet: 40
  • Air Screw: Around 1.5 turns out, constantly adjusted by eighths of a turn to suit seasonal and daily air density fluctuations. This allows bike to idle a bit more reliably (it had never had the head machined properly to match the big-bore, so was temperamental when idling) and to pull cleanly off idle.
  • Throttle Slide: Stock #6, but ground with a rotary stone to give about 7-8mm of cutaway, approximating a number 7 or 8 OEM item.

Some good carby information is available at Eric Gorr's site and some useful charts at Sudco is a good place to buy carby parts in the US. Show and Go is the Australian Keihin distributor. James Dean's Keihin Jetting Guide is an amazing Excel spreadsheet for PWK (and FCR Four Stroke) carbies. Ben Rush has also taken the trouble to make a nice KDX-to-Keihin jet needle decoder spreadsheet. Jaguar maintains a helpful page devoted to international SR model KDX200s.

My Engine Modifications:

  • FMF Gold Series Fatty pipe (K-14)
  • FMF Turbine Core oval muffler
  • 240cc big bore kit
  • Uni filter Airbox lid opened up
  • Boyesen fibreglass reeds
  • Big car-type inline fuel filter

Other Modifications:

  • Bark Busters
  • Renthal handlebars
  • Stainless steel footpegs
  • Pipe guard thingo
  • Ceet stickers


13/45 with 19in rear wheel. Big-bore engine pulls taller gearing easily.


Copyright © Craig Forsythe, 2013. All rights reserved. Contact.