KDXRIDER.NET

Last year was my first riding dirtbike and single track. I bought a 2011 Husaberg 570 because it was street legal and would still work well on single track. Although it was a great bike, it was a handful in the tight stuff... way too much bike for my riding level. I seemed to spend more time laying on the trail than I did sitting on the bike. I sold it and decided to buy a cheap 2 stroke.

I found a 2001 KDX 220R, which although dated, has as great reputation for reliability and rideability. People rave about the power delivery and wide ratio tranny for woods riding. The biggest draw back is the less than stellar suspension, mainly the conventional forks. KX125/250/500 USD fork are a pretty common and easy swap. I started researching the project and pricing parts. Everybody seemed to want $500 for forks, triples, axle, rim and brakes. After that I would still have to have them revalved and resprung...another few hundred dollars.

While searching for forks I kept seeing late 90's early 2000s KX bikes with blown motors for the same price as most people were asking for the fork swap parts. I ended up buying a (what I thought was) '98 KX250 basket case for $325.



The plan was to stick the KDX220R motor in the KX frame. I know most people would wonder why anyone would bother messing around with such a project when 2005-2008 KTM 300s can be had for $4000-5000 all over the place. Surely I'll have to put thousands of dollars into it to even get it equal to a 5yr old KTM... so why bother? Well, because I have this mental illness that causes me to f%^k with everything. I can't just leave well enough alone. In that past that's been Chevy V8 swaps into Toyota pick-ups, 4Runners and Landcruisers. A 12valve Cummins swap into my Ford F450 and most recently a 3.4L quad cam Tacoma motor into my 94 4Runner. Messing with things is just in my blood.

The pile of parts above was Sunday March 17th. Things came together pretty quick.

The KDX getting stripped:


Piecing together the KX250 bits was a bit of a hassle. Buying a basket case is rough sometimes. You don't know the order of assembly, which spacers, washers, nut and bolts go where. Fumbled my way through.


Realizing that Dave had given me the wring triples for the bike:


Bye bye KDX:


Not sure why I weighed it but 51 lbs:


The biggest hurdle is modifying the KDX engine case and KX swingarm to work together. The through hole on the KDX case is 15mm and the KX swing arm pivot bolt is 17mm.





Some people take the engine to a machine shop to get it drilled on a mill to ensure it's 100 straight. I opted to buy a 17mm bit...$80...are you kidding :eek: I took my time, set up a jig and drilled it myself with no issues.

The next challenge is the width of the KDX engine boss is wider than the inner span of the KX swingarm.



Some trimming was required. Both sides of the 99-02 swingarms are like the right side of the 94-98 swingarm shown here:


On the 99-02 KX, you can simply trim the pivot area back and call it a day. The '98 swingarm requires some more thought and TIG work. I figured I need to cut 11mm off each side. These cuts aren't critical, they don't need to be perfectly square so the grinder and zip disc are all you need:


Had I known how thick the material was before I marked my cuts, I could have planned it out better and saved myself some TIG welding later. I know for next time.

FIller piece that will get welded in to cover the hole:

The new swingarm pivot bearing and sleeves are too long for the modified swingarm. The opening is 52.4mm per side and the Moose pivots are 60.3mm. Bust out the grinder and zip disc again to remove 7.9mm from the pivots. These cuts are critical so they had to be totally square. Measured, marked, rechecked, cut 1 mm to long and ground to final spec with a flap disc.


I wish everything in the garage turned out this good:


Motor mounts:

The factory 250 mounts had to be cut out and replaced.


With the motor support and centered with the swing arm pivot bolt, measurements for the new mounts and headstays could be taken:


I didn't have 1/4" aluminum to make the new head stay brackets so I used 1/8" steel:


Knocked some lightening holes in them with the press:


I'm missing the finished product pic...will take another tomorrow.

The KDX (depending on year) uses a front or rear or front AND rear head stay set-up. Mine had front and rear.
Head prior to surgery:


The rear mount doesn't let the tank drop into place:


Again out comes the Sharpie marker and grinder/zip disc. I get halfway through the front head stay before I realize that I'm cutting off the one I need *palm on face moment* It's 4am, clearly time to call it a night.

Monday evening I head back out and cut off the REAR mount. I'll have to pull the head and get the front mount repaired when I take the swingarm in for welding.
Rear removed (cut visible on the front):


The head now clears the fuel tank by 1/4":


With the old motor mounts out I fabbed and welded in the 4 new ones (upper 2 visible). The motor fits and looks like it cam from the factory that way.


A test fit with the exhaust...close but not close enough. The front tubes on the 250 frame stick out farther than a 125. The neck on the pipe needs an extension to fit in the 250 frame I'll take better pics when I tackle it.


With all the welding done I could paint the frame:


Start stuffing junk back in:






There's a few bits and pieces I'm missing but they are on their way:
Seat
Rads
Chain
Pipe -FMF Gnarly Woods
Linkage pivot kit
Full plastics kit

I cleaned up the old plastic with a Mr. Clean Magic Eraser... TRUTH IN ADVERTISING! Absolutely amazing! I can't believe how good they look compared to when I got them. Had I know they'd look this good I wouldn't have ordered new ones :eek:


I have a few more things to install once they show up but it's currently 195lbs. Hoping it'll come in under 225lbs.


That's where it sits after a week of casual evenings. Probably 15hrs so far. The suspension is out and being revalved and resprung tomorrow. I need to drop off the swingarm and head for TIG welding tomorrow as well. The new pipe is here now.

All the parts needed are paid for and I'm into the bike for $3203. For that I have custom set up bike for me with new:
-grips
-hand guards
-chain
-sprockets
-swingarm bearing and seals
-linkage bearing and seals
-front and rear wheel bearing/seals/spacers
-brake pads front and rear
-plastics
-rads
-chain guide and slider
-brake pads front and rear
-pipe
-silicone rad hoses
-Rebuilt, revalved and resprung forks and shock w/titanium spring.

I think I did pretty good for $3203 and I still have the KDX parts to sell

If I was doing it again I would hold out for a 99-newer KX125. The stock KDX exhaust fits without modification and the swingarm can be trimmed without any welding required (with careful grinding the welding may not be needed on the 94-99 either).

I post up more when my other parts show up.

I'm waiting on parts still. Dropped my swingarm and mis-cut head off at Trillium and should have it back Monday. My forks and shock should be back Friday.

I haven't been looking forward to the exhaust work. The neck needs to be extended about 3/4". I thought about cutting and welding a piece in but I hate doing things like that. I would rather make an adapter/spacer that can be transferred from pipe to pipe. I know bashed pipes can be repaired but I'm guessing at some point they end up just needing replacing. By building a spacer, I can simply buy a new pipe and install it rather than f%^king around and welding extensions in.

There are a couple of M8 holes on the side of the exhaust port that I thought I could incorporate into the extension/spacer:


I painted the surfaced and stuck a piece of paper on to get the layout, not perfect but close enough:


Transfer important locations through the paper with a with a punch, sketch with Sharpie, cut with zip disc (man I miss my plasma cutter) and check fit:


I measured up the ID of the port, the OD of the pipe, the ID of the spacer and all the bits and pieces of scrap tubing I had in the garage and didn't like where things were going. It looked like there was going to be lathe work involved. I like doing as much as I can in house and since I don't have a lathe I decided to find another option. I cut the neck off the mangled stock pipe:


It is perfect actually. The o-ring grooves are already there and the length is 3/4". The ID is just smaller than the ID of the new FMF unit. I cut a piece of 1.5" aluminum tubing. It was too big to fit the spacer (neck= 1.47") but a 50 ton press can be quite persuasive



The fit of the spacer into the FMF was tight but went with some CopperCoat and a mallet:



There's a factory dent on the pipe to clear the ...whatever that thing is...but I needed a bit more to get things lined up:


95% of that crater was already there, I just had to tweak for the corners of the...what is that thing anyway??


Fits like it was made for the frame now:





I'm anxious to get the suspension and swing arm back so I can assemble that stuff for what should be the last time. ETA on my rads, plastic, linkage kits and seat is April 11th...ugh

BTW, I'm terrible at proofreading my own work so apologies for the typos and mistakes.

Wow, I'm very impressed! I'm fairly sure I haven't seen this done with a 250 2t chassis. I love the way the engine sits in there.

It fits well. The exhaust being the only real not fitting part but that was easily sorted out. I think next time I would do a 99-newer 125 like everyone else to avoid the extra swing arm work and exhaust mods.