1998 KX 125 rebuild/restoration (tons of pics)


Apr 4, 2005
Howdy howdy everyone. I've already got a dirt blog going on about my new found misery, but I thought I'd start a thread here to get more feedback and maybe someone will chime in with something I'm missing, or something I'm doing wrong.

The Bike

I bought this bike a year ago, it's my first bike. I ride motocross primarily, and plan on racing arenacross this fall/winter. Beginner level rider, expert level ego. :)

How It All Began

I was loading up about 3 weeks ago to spend a night out the track, as I was tightening the tie downs, I heard a very suspicious clunk come from the forks. I knew that this wasn't going to be good. I pulled the fork caps and the left fork leg was in disarray. The top collar was in two pieces, the piece that sits inside the top of the piston assembly (not sure on what it's called...it's about a 3 inch long little pin) was not in place, and the piston rod assembly wasn't even attatched to the cap. I knew this was way out of my scope of repair. I called up Marshall's Racing which is a great shop in the state of Oklahoma and he told me to go ahead and bring it on by to inspect the damage. Turns out the entire rod assembly was bent. This makes perfect sense of a problem I had last year when I changed the fork oil.

I was trying to get the cap on and could not get the thing to thread. If I just put the cap on without the rod assembled, it threaded fine, otherwise it would not thread. I somehow got it threaded, I had no idea the rod was bent.

Anyway, the assembly is running me $250, so Marshall's is fixing the fork, and I sprung to have the forks and shock revalved and resprung since they cut me a truly sweet deal.

Now that my bike was half apart, I decided to go ahead and pull the swingarm, linkage, and steering stem to replace the bearings and seals.

Then, I decided since I was going to that much trouble, I might as well get it down to the frame and slap a nice coat of paint on it. Somehow along the way I've decided to restore this bike to pretty dang close to perfect.

The Reason

So why am I restoring an 8 year old bike?? Because I'm poor and don't want to spend any more money on a new bike. This one is paid for and college is expensive. I plan on keeping this bike until I get done with college. I might as well have it look, run, and perform like it should and is capable of. Besides, I think this type of thing is fun as I enjoy wrenching. Furthermore, I've got the time right now to do it. Most people do this type of thing during the winter, but I'm going to be down for jaw surgery this summer and after that I'm working 60 hours a week. No time to ride as it is. Another positive is this is my first bike, and I've only been into the sport a year. This gives me a way to learn about how my bike operates the best way I learn. Tear it apart and put it back together.

The Plan

Revalved and resprung suspension for my weight and skill
Paint frame and subframe
New wheel, swingarm, linkage, steering stem bearings and seals
New plastics
New graphics
Fastway footpegs (I'm 6'4, need to drop them)
Tall seat foam
Gripper seat cover
Repack silencer
Have carbon removed from expansion champer
Rebuild top and bottom end
Polish swingarm (yes, I know bad idea, but the paint looks awful)
Black rims to get a little bling
New front tire
New chain and sprockets
Radiators straightened
Replace any and all broken/missing pieces (i.e. - rear caliper guard that's broken, random bolts that were zip-tied, missing radiator guard)
*I'm sure this list will grow, I know I'm leaving stuff out.

All pieces will be thoroughly cleaned and inspected before they're put on the bike.

And the pics....in chronological order.

Before the madness


It has begun.





Apr 4, 2005
I didn't get pics of the finished frame stripped because my camera's battery died, but I got 95% of the paint off, and got the rusty areas nice and pretty again




Got some PJ1 on the subframe...halfway done

And that brings us up to speed! I'm going to slap on one more coat of primer on the frame and then get to wetsanding. Then comes the paint, and then clearcoat. Someone to remind me to get clear background tape when I'm done to put on the boot areas.

More to come....stay tuned and offer me lots of support, cause I could use it. :bang: Senior KX Rider's beautiful 97 KX 144 is great motivation for me.


Jul 11, 2005
If you had the money powdercoating would be awesome. From the pics it looks as if your spray painting it. Which could turn out great but im not sure about how durable it would be. Check out powder coating,it would last forever. Good luck it looks like your doing a good job.


Apr 14, 2002
Good luck. I think the swingarm idea is great. I don't know why they paint them in the first place. I used several coats of paint stripper on mine. I didn't get too crazy with the polishing. In fact I took some sand paper and went one way to make a pattern. It seems like its easier to keep looking good than if you tried to keep a mirror finish on it.


Apr 4, 2005
Thanks everyone. I'll put up some info as I was researching frame painting that I've come to the conclusion of.

Powder coating would no doubt be the best bet, but it did have its drawbacks.

1.) The frame is 8 years old. I'm concerned that if there was a crack, I wouldn't be able to see it as easily or at all with a powdercoated finish. I also couldn't match the factory frame color like I wanted. I was weary of switching frame colors.

2.) From what I've readl, PJ1 should do a good job with the paint as long as you prep the surface good and do things right. That's why I spent well over 20-25 hours stripping paint. Which brings me to my next point.

IF YOU'RE GOING TO STRIP YOUR FRAME AND PAINT IT, PAY SOMEONE TO SANDBLAST IT!!! I spend so much time stripping paint it was ridiculous. I tried all different kinds of stripper. Automotive, cheapo, and the high powered stuff. Aerosol, brush on....it was ridiculous how some of the paint would just not come off, especially in the tight corners or on the welds. I don't have any power tools, so if you got better tools than I do (a wire brush, razorblade, steel wool, and too much time on your hands), you may have better luck than I did, but yeesh! Talk about a PITA.

I'm not expecting the paint to stay perfect. I know it's going to get scratched and chipped. I just want it to look better than it did, and it gave me the chance to really inspect all the metal to be sure there were no cracks or major problems.

3.) I'm poor, and would rather $$$ spend the difference between DIY and powdercoating on more important improvements.

4.) From everything I've read on epoxy paints, they're extremely tough paint, and I plan to use many coats to keep it from rubbing off to the bare metal. My theory is if I slather on the clear coat, it's just that much added protection from rubbing off. Combine that with clear background tape where your boots rub, and I think I should be pretty well covered.

The pics that show the bottom of the frame.....man I don't know what terrain the previous owner rode, but there is no paint at all there. It looked nasty. It looks like tried to ride over boulders all day.

The swingarm should be much easier to strip. The paint is much softer, and the large flat surfaces will be easy to strip. I don't want to spend the time to keep the thing looking like a mirror, but I think dull aluminum would look tons better than the crappy paint they put on it. It's scratched, dirty, got gunk all over it. It's awful looking. And if it starts looking bad, I'll just throw some polish on it and shine it back up.


Mar 15, 2005
Looking nice man. I did the same thing over the winter. Stripping is ALOT easyer with a wire brush drill bit and drill. That how I did mine. I know its a little late, but for next time I guess lol.

Your bike looked pretty good before, Its gonna look really good when its done. Cant wait to see it! Keep us updated!


Apr 4, 2005
Got a bit more done.

Here's my nice newly blinged swingarm. If you have the right tools (a drill with a wire brush) you could easily do this in an hour once the swingarm is off. The bare aluminum looks eons better than the paint, and I just polished it really quick. I don't care if it looks like a mirror or not, just gonna get dirty anyway. As long as there's improvement over what it was, I'm happy.

I got 99% of the paint off pretty quickly. I may still take the dremel to a couple tiny spots, cause it's probably going to bug me if I don't get it. I just wanted to get out of the shop and decided to snap some quick pics before the rain comes.




And here's the painting I got done today. Well over half way finished.


After I get this painting done, I'm going to be 2 hours way at home for 3 months. I'm taking the motor with be and it's getting a rebuild I guess. I talked with Marshall's today and I'm going to find prices on the crank assembly....apparently OEM is my only option, no aftermarket for it. :( Once I tally up the price on that I'll decide on which to do first.....order new bearings and seals for the steering stem, linkage, and swingarm, or start on the motor. Once I get the motor and bearings and seals done.....I can finally get this thing looking like a bike again!


Nov 4, 2005
Hey Assist, I tried to PM you but it won't let me for some reason. Anyway, I have a 98 RM125, which once I return from being deployed, is going to get the same treatment you gave your KX.

I stumbled across your thread doing a search, and glad I did. By the way, thanks for all the pics. It makes learning so much easier. Can't find enough of that on this forum it seems like. Maybe just not looking in the right places, who knows.

From the pictures, it looks like you're in the same position I'm gonna be in once I make the move back home; garageless. :( Can make finding places and time to wrench a chore.

I was hoping to be able to contact you for questions and such on your experiences and findings. I definitely know my way around a tool box, but have little experience with dirt bikes.

If you don't mind, shoot me an e-mail and hopefully you'll let me pick your brain a little. Alright thanks alot and hope to hear from you.




Jul 17, 2006
Dued, you said that you are poor, but how can you afford to do all of this stuff to your bike?
Wouldn't it have been cheaper to sell up and buy a bike in better condition?


Play with gravity
Apr 26, 2004
AssistSuper said:
The pics that show the bottom of the frame.....man I don't know what terrain the previous owner rode, but there is no paint at all there. It looked nasty. It looks like tried to ride over boulders all day.

That portion of frame looks just the same as yours on my 00 kx 125! I guess it's normal. Your project grabs my attention because I was planning on selling my bike next year, but if I could get it spanking new... Hurry up to post follow-ups!


Oct 9, 2006
I use Aircraft Remover available at any Wallymart store.I don't know if that's what the author used,but it does the same thing.Just don't get the sh!t on yourself! :yikes:


Nov 14, 2006
As I was reading your post I kept saying no no don’t do that! You made all the mistakes I made my first couple of rebuilds. For your next rebuild: If your keeping the same color and using rattle-cans then there's no point in stripping off all the factory paint, in fact your better off leaving it on. If you clean and wetsand the existing finish with #400 before you paint, then it will look just as good. Also when your paint chips (and it will chip because spray-bombs are not nearly as good as the original paint) there will probably still be factory paint under it, making the chip less noticeable.
Because your bike is 9 years old and you had it all stripped down, you might as well have gotten a welder to gusset the area where the bottom frame tubes butt to the linkage bracket, and complete the welds on all the seams and mount plates (This advice in this last sentence was taken from Eric Gorr’s book)
Other than that your doing a great job. I really like what your doing with the swing arm, I’m thinking of doing the same thing to mine. Check out a bearing shop for chassis and transmission bearings, you may get them cheaper. Wiseco should make a connecting rod kit for your engine. Good luck, looking forward to seeing how it turns out.

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