KDXRIDER.NET

i should be completed in a couple of weekends. here is the start:

bike 1997 kdx220 (using a 1993 kdx E for mock up)
forks 1994 ktm 300 mxc usd white power form left stamped K23M94US

plan: press out kdx and ktm stems, replacing the ktm stem with a shimmed kdx stem

the ktm forks the same bearings for upper and lower positions, which are skf #332174, and measure 29x50x14 mm.

the kdx forks use upper bearing 25x47x15 mmand lower bearing 33x55x17mm.

at first i pressed the kdx LOWER bearing on to the ktm stem with a 1/2mm piece of shim stock to take up the difference in sizes between the kdx bearing and ktm stem, then slid the forks into the test bikes frame. finally i dropped the stock upper ktm bearing into place, and tapped the upper triple tree into position.

results: the lower bearing is a good fit, but the ktm stem is too short, and also to large an OD to allow for the upper kdx bearing. this means the wider ktm upper bearing is too wide, and doesn't fit the smaller kdx race that is pressed into the kdx frame.

i used .010" brass shim stock wrapped twice around the ktm stem for the test fit. the bearing is snug enough to test. I'll use brass for the final assembly also.

this week i will press out the kdx and ktm stems, then shim the kdx stem fit the ktm triple and press it in to the ktm triple. making up the difference between the kdx bearings and the ktm steering stem will also be brass shim stock.

why these ancient ktm forums, that will require a ktm front wheel/axel/brake caliper that is different from everything Kawasaki/Suzuki/etc makes?

because they are fully adjustable compression/rebound, and i paid forty dollars for them and the rear shock, and they are massive compared to the kdx spindles.


I'll update with pictures after i press things together.

GOOD LUCK!!

yesterday i dropped off the triples to have the kdx stem pressed into the ktm triple. after some quick measuring it appears the stem is the same size at the Los fit, on both stems. if that is the case I'm only a few eBay parts away from a fully adjustable front end. pretty excited about riding across ruts instead of wiggling through them like a half dead fish!

I'm going to hold off on ordering a caliper and wheel until i know the stem swap was successful.


the 1994 ktm 300 mxc (white power) forks in question:


fork model stamp on top of fork tube:


test fit with kdx bearing on ktm stem (top bearing prohibited real fitment, this is just a test!)


compression adjustment (i'm going to jbweld a ring around this to protect it some)


rebound adjustment (woohoo, on the fly!)


kdx stem bearings (original?)




cool fact, the bearings were in place for so long that they imprinted their brand / model stamps into the triple tree!


here is the kdx LOWER bearing test fit on the ktm stem, this is NOT the final setup!


if you're confused now, the ORANGE marks are for ktm pieces, the GREEN marks for kdx ;-)


for comparison, this should be a decent stability improvement judging by the stancion size increase


stem length difference


the ktm stem uses the same size bearings top and bottom, which means there are two fits (with an undercut in between) to pull the lower bearing over. here i used a simple puller to pull the lower bearing up over the top fit. it's a very light press, if you can all it 'press' at all. if you need to do this CLEAN the areas around the fit to prevent scoring the soft aluminum stem !

ok, update time.

i dropped off the ktm and kdx triples at a local shop (will remain nameless) to have both stems pressed out and the kdx stem pressed into the ktm lower tree. unfortunately they took a week to finally do it, and in process damaged the threads on the kdx stem that the top nut screws onto. i was disappointed, but carried on. i guess they didn't know to put the nut on the stem while pressing, and fill the hole with something solid like an aluminum plug to prevent warpage. anyway, you live and learn, i hope. :)

the kdx stem is about .001" smaller than the ktm lower tree. that means it won't press in. boohoo number two !

I'm going to use loctite 608 (or similar) to glue the stem into the lower tree, and let it cure for a couple days until touching the setup again. i'll do this with all the triples/forks/stuff aligned in the frame so that nothing is off kilter in the process. yes, glue, if you're unsure about it, read up on some of the loctite series of glues and their tensile strength. it's going to be ok, i promise ;-)

anyway, here are the parts i've used top to bottom:
stock kdx upper nut
stock ktm upper triple
notice i deleted the stock kdx preload nut, more on that later
stock kdx upper bearing
stock kdx stem
stock kdx lower bearing
stock ktm lower triple
stock ktm fork legs /wheel/caliper/etc stuff. i have to order these parts, but you get the idea.


on to the pictures




notice the stem is hanging down from hte lower triple, it will be flush once i glue it into place, this is the mockup still ;-)


i'll probably make an additional dam/seal for the front of the lower bearing out of RTV at some point, but the stock kdx lower seal is there, and happy. :)


i may end up cutting the upper bearing preload nut in half to make clearance for the assembly, or just leave it off completely. i dunno. no biggie.


you probably can't tell now, but i had to thread file the stem's threads forever, and then lap the threads in order for them to be smooth enough to install the steering stem nut by hand. man that was annoying and monotonous work. if you ever have sticky/bad threads that aren't damaged enough to stop the nut, you can put rubbing compound (car polish stuff) on the threads and work the nut back/forth with a crescent wrench, about 1/4 turn at a time until it laps the threads nice and smooth again, without loosing any engagement. i did this for the entire length of the threads, which are smooth and tight, like they should be. works for corroded old bolts too. take your time, it will be sweet when you're done.


i still need to order:
ktm front wheel
ktm caliper
some fork guards

once those arrive i'll slap it all together and go for a ride. keep in mind this is an E model i'm test fitting everything on, and my H is just DYING to get this upgrade bolted on to it. I intend to complete the setup, test it for rigidity, and then transfer everything in a saturday morning for a nice test ride on the H.

i would give this fork swap a 3/5 on the difficulty scale, but only because the shop messed up the threads, and i know a lot of people aren't comfortable with repairing threads or similar almost-machinist work. i am.

honestly this would be about a 2/5 if someone had a harbor freight press and a map torch, but i only have the torch.

thanks for watching, i'll update again soon.

loctite 680 smeared onto the stem and triple tree, they are not coming apart without a bunch of effort now ;-)

OK i just slapped it all together. man if i knew it was this easy to change forks i would have done it the first week i owned the bike!

waiting on shipping : 260mm rotor for my kdx wheel, and a caliper. should be riding this next weekend!

none of this is sprung for my weight yet, but it should be a massive improvement

all i need now is to bleed the brakes.

i used the ktm axel, the kdx wheel, picked up some 35x17x12mm bearings so the only change made is a sweet of bearings to go from the ktm forks to the kdx forks.

i pulled it off the stand and jumped around on it.

holy crap these forks are plush!!!

the magic clickers are really nice to, OK time for some brake bleeding....

first test ride (Street) is in the bag. I'm very pleased with the 260mm brembo brakes and the standing position is even better now. over all the rigidity of these forks is a vast improvement. crossed ruts are nothing. I'm very happy.

i rode the same single track this morning that i have for about 9 months. the rebound damping wasn't aggressive enough, it actually felt just like the old kdx forks, but without the spagetti wiggle. three clicks on the rebound knob and it was much better. i added one full turn to the rear shock preload, and tried again.

almost there....

two more rebound clicks and rode the same section of trail with up and downhill areas with about 10" logs halfway up and down. man what a difference, instead of deflecting left/right or unpredictably, now it just GLIDES over the logs, and doesn't matter if i'm climbing or descending.

the stability at speed is fantastic, no headshake at all (wasn't expecting it anyway given the sag in back) and the bike really enjoys carrying more speed now. there is a definite difference between plodding along and having to fight the suspension vs carrying speed and letting it smooth things out.

the only thing i was worried about was the reduced bar sweep, because the forks were designed for a single spar frame, and my H is a double. after riding TIGHT singletrack today, i have no worries about that anymore. it performed wonderfully, soaked up everything from stutter bumps / braking bumps / logs / g outs, and everything in between.

very happy !

if anyone has specific parts they was highlighted or described in detail just ask. :) go do it !

I just put a 2004 KTM exc front end on my kdx...Fairly easy...I'll upload a pic when I figure out how on here

UPDATE-

After a year of riding the WP ktm300 forks, I'm very happy with them. I have not bottomed them once, even with all the preload released. I did change the fork oil a few weeks ago, to atf from the whatever-stinky-stuff was in there. Nice plush improvement. I really would like to improve my decreased turning radius that the ktm300 wp forks has...

So I bought a kdx E model parts bike, that happens to have kx250 (I think?) forks on it.
The good: it came with good wheels (huge bonus), forks, clutch basket (SCORE), and it appears the bottom end is ok, minus the con rod. Oh, and the power valves are good.
The bad: the kx forks were never properly installed. ie: instead of a stem swap, they just used the lower bearing, and tightened down the nut in place of the upper bearing. yep. Sure did. Soooo, I'll be reading the stem swap threads here about the kx250 forks, and deciding if I want to go that route, or just sell it all.

Thanks for the update.

Surprising fit on the KX forks. Crazy

well whichever way you go lemme know what ya got leftover kyle as fixing my front forks has now taken the center stage as there isn't anything left other than the eventual engine rebuild left.