KX to KLX Fork Swap
Process and photos by Bruce Brazil aka Brewster
Mechanical Drawings by Adam Reif
Web Page Layout by Billy Dean

There are a few mods that we do to the KLX300 to improve the power to the ground, like changing the carb, head pipe, countershaft sprocket, and the Free Mods.   But the real weakness of the bike is in the suspension.   The KLX was originally designed as a dual sport for the Asian and Australian markets.   The stock suspension setup is not very good for off road use.   The forks are set up for a 140 lb rider and the shock spring for a 185 lb rider.   The internal valving at both ends leaves a lot to be desired, and there is not much to work with in the stock fork valving.   So the standard upgrade is to install Gold Valves and springs from Race Tech to match your weight.   But only the compression valve gets replaced, because the rebound valve in the KLX forks is a sealed unit.   So even with a Gold-Valve mod, you still have no rebound "clicker" in the forks.   In the never ending search for ride improvement, I decided to try a set of KX forks.   The forks I used were from a '94 KX250, but the Forks & Triple Clamps from several other years and models of the KX will work for this project.   The RESULTS: a better front suspension than the KLX with dialed-in Gold-Valved forks...


HIGHLIGHTS OF THE PROJECT


GENERAL INFORMATION

I wanted to retain the steering geometry, didnít want to change the ride height, and wasnít concerned about increasing fork travel.   The KLX300 and 1994 KX both use 43mm forks, measured on the outside diameter of the lower leg. And the diameters of the mounting areas of the KX forks are the same as the KLX.   But the length of the forks is different, the axles are different diameters and mount differently in the forks. A KX axle and front wheel could be used, but to retain the stock KLX axle/wheel/caliper/rotor assembly, custom spacers to reduce the length of the forks and custom axle bushings are required.   Thanks to Adam Reif, we have fully dimensioned fabrication drawings for these custom spacers.   Install Adobe Acrobat before you attempt to download the... FABRICATION DRAWINGS

When machining the left axle spacer, make sure that the internal threaded portion is concentric to the outside of the spacer. I hand tapped mine, and it wasnít lined up, which would have caused problems with the alignment between the brake rotor and caliper. I ended up screwing the spacer onto the axle, and then mounting that onto the lathe. The large end of the axle went into the chuck and the other end onto a dead center in the tail stock and then turned down the outer portion of the spacer. The photo of the Left Axle Spacer is different than the mechanical drawing because of my "corrected" bushing. Use the specís in the mechanical drawing.

The upper steering bearing and upper part of the steering stem is larger on the 1994 KX so I stayed with the KLX triple clamps. The lower KX triple clamp has two bolts on each side to hold the fork tubes, a stiffer configuration. I considered using the KLX steering stem in the KX triple clamps but was unable to press the KX stem out and the KLX stem has a roll pin holding it in. The roll pin goes into a blind hole so you canít push it through unless you drilled through the other side.


PROCEDURE

»  Iím not going to go into detail on how to remove and disassemble the forks. There is a good write up in the HOP UPS section of PlanetKLX under Gold Valves   But I would recommend that you replace the oil seals and lower bushings for the KX forks. The photo below shows the lower bushing, the upper bushing, the washer, and the oil seal.




CAUTION => this aluminum part sits right under the fork cap. When putting things back together, the end with the holes goes down into the fork.




»  Remove the compression valve with a 14mm hex wrench and cartridge holding tool...




»  This is what the cartridge holding tool meshes with to hold it...




»  This is the KX compression valve.




»  Near the middle of the fork rod on the KX, is a fixture that screws together. On the KLX, this piece is held in place by a crimp and shouldnít be removed. Unscrew the two pieces of the fixture.




»  Watch out for the two half circle pieces of hardened wire.




»  The fork rod can now be slid out of the cartridge. The rebound valve is on the end of the fork rod.



»  Clean everything. I used kerosene to flush the forks.

»  If you want to use the stock odometer, you must make something to hold its position relative to the fork. The stock KLX fork has a stub cast into it for this purpose. I measured its location, transferred that to the KX fork, and drilled a 3/16-inch hole and inserted a spring pin, 9/16 inch long. Be careful drilling the hole so that you donít drill into the cavity of the fork.

»  Slide one of the fork spacers onto the fork rod. The taper guides it into the top out spring that is still in the cartridge. No, I donít know whatís holding it in there... :))




»  Put the fork rod back into the cartridge and reassemble the fixture. The two half circle wire pieces must be in the groove on the fork rod.



»  To put everything back together, reverse the order.

»  Before you put the spring in, add the fork fluid. I used the same measurement as for the KLX, 100mm from the top of the compressed fork. Be sure to slowly pump the fork rod to distribute the fluid and get the air out.

»  The stock .38kg KX fork springs are too long. Use the springs from the KLX. They are the same diameter and are the correct length. Iím using .40 kg springs for my 155 lbs.

»  With the forks reassembled, they can be mounted in the triple clamps. I located mine so that the groove near the top of the fork lined up with the top of the triple clamp.



»  Before you mount the front wheel, insert the custom axle spacers, axle, and tighten the axle caps just enough to get rid of the clearance. Left and right is relative to looking at the forks from the riders position. The slot in the custom right axle spacer should line up with the separation between the fork and axle cap. Push the custom left axle spacer's flange up against the fork, and check for a flat fit. I had to grind a little of the fork away for proper fit. Tighten the left axle cap.



»  You can mount the brake caliper now or after the wheel is in place.

»  Install the front wheel and odometer drive.

»  Donít forget the stock spacer on the left side of the wheel hub.

»  Snug up the axle so that everything will be pulled to the left fork and then tighten the right axle cap.

»  Gas her up and go for a test ride... :))