Rebuild 99 KX 125 Worth it?

[Sully36]

So I'm new here and figured I would start with a basic question (that is actually much more than basic) I acquired a 1999 KX 125 from a buddy a few years back because he didn't have time to get it working. He did own it while it ran so it was a fully functioning bike at one point (maybe 8 years ago now) Well I determined the main problem to be a broken clutch pull (The part that connects the cable through the case) Back then I didn't know much about engines/carbs so I ordered a carb off eBay and tried that. I got it to start once with a rolling start. I opened the throttle...and that’s where it stayed. It ran at WOT in first gear for about 2 minutes until I shut it down. This was probably 4 years ago. It’s been stuck in first gear in the shed since. Before that, my buddy owned like I said and rode it on trails for about a year and before him, a guy used it to race I believe. It had its rear shock overhauled a couple months before I got it.

So fast forward to today. I have started thinking about getting into riding again; possibly try out some local motocross tracks that have opened up since when I stopped riding. Maybe even see if I can get into some amateur races.

My main question is, is it worth rebuilding this KX or going out and buying a 250/450 4 stroke or just even another running 2 stroke?

I have kind of been figuring a complete overhaul on this bike to get it back to "like new" power/drivetrain wise at least. I mean everything from a new carb parts (solenoids and what not that came on the 99-00's) to the top end (new piston, re-plating if needed) down to clutch and crank bearings. So if I did all of that, is the bike still even worth it? What things should I definitely just order now before even tearing it down if anything? What parts would you guys recommend replacing and what could just use a cleaning (like carb body and maybe all the internals)? Should I rebuild Suspension? What parts should be aftermarket (and what brands) and what stock if I want a "bullet proof" race platform. (I know bullet proof is impossible with these and they will need to be rebuilt regularly but you know what I'm getting at)

Thanks for the advice, help or the slap in the face if I'm coming off as dumb for wanting to fix this one instead of just buying one. (Which I'm not opposed to but would also like to learn a bit more about bikes from this one so if the scales tip only slightly to a new platform, I may not be opposed to a rebuild)
 
BTW, I am a home mechanic and can handle most stuff that doesn't require special tools/training so most things I can pick up. I've just never really messed with Carbs.

[yeomans]

I'd say it worth it man.
I ran the 99 kx 125 fresh out of the crate in 1999, it's the first bike I ever rebuilt myself.
I now run the 99 kx 250 and I am doing a 99 250/500 conversion.
Don't quote me on this but I believe both the 250 and 125 L series (99-02) bikes won the Motocross Action shootout in 1999.
I can't say enough about the handling on these bikes. Maybe its just my personal opinion but it felt like my kx 125 was on rails.
Different strokes for different folks. If your a home mechanic and this is your first bike rebuild go with the two stroke bike,for price reasons and rebuilds are easier.
Get yourself a manual and pop on this site for your other questions.
Get yourself a set of v force reeds and a pro circuit pipe, its a nice crisp set up on those bikes. These bikes came good out of the crates, not to many hop ups are needed to get out and ride some local events.
Check out your weight before doing anything with the suspension. If you are somewhere around 180lbs you might just get away with some new oil and seals.
Just what you'd learn by tearing the motor apart is worth it alone.

[Sully36]

^ Thanks for the tips! I should have mentioned it has some performance parts from the previous "racer" owner. Pro Circuit Pipe. And the billet clutch basket are two things I remember off the top of my head. I suppose its possible he upgraded the reeds as well but I'd have to double check.

I'm about 155-165 depending on the week. Think I could get away with them for awhile or should I just change out the spring rates while I do the seals and oil?

[yeomans]

You can check your springs rates using race tech suspensions website.
They will tell you what springs came stock on the bike.
Chances are you won't have to change springs because most manufacturers spring rates on 125's are designed for people in your weight class.
Doing a rebuild on this bike might seem overwhelming at first but, you can do it,and have a sweet bike and save yourself some money to keep racing/ riding with.
Plus 125's are a blast to ride.

[GREENKAW24]

Yes its worth it. Restored this '99 in 2010.

[GREENKAW24]

The 99-02 are great handling, have a great ergonomic setup IMO, and I love the look of them. Mine is now a 144 big bore, soon to be 155 big bore stroker. (Racing the 200cc Hillclimb class)
The 2000 cylinder is the best as far as port layout. Mine does have the 2000 cylinder on the 2002 cases (need to be matched). Has a flywheel weight (needed), and 2002 ignition (digital).
I've switched between a 36mm and 38mm Mikuni TMX, and it has a Pro Circuit Works pipe although I'd rather a FMF Fatty for the big bore. Alot of our hills and tracks out here are sandy and the flywheel weight, 36mm carb, FMF pipe, Shorty Silencer work better for hookup and power in sand.

[USMC 500]

Honestly, if you want to get value out of the bike its not worth it.....Rebuilds are money pits......I just finished a frame up (bearings, motor, suspension, plastics, and everything new) and I can't get back what I put into it........that being said, if its a rebuild for you then money has no value.....There is nothing like the feeling of a bike that has 99% new parts on it.......My 98 KX500 feels better and tighter that it did coming off the show room floor.......I say do it.....you'll love it.

[KevinTwoStk]

I'd say rebuild it only if you want to keep it and ride it. I'm enjoying my '00 KX125, play riding as well as racing Vet Novice in the District 37 Big 6 GP series. The photo is from the Hilltoppers GP last weekend in 29 Palms.

[Sully36]

I definetely plan to keep it if I do all this work to it. It wouldn't be something I would try to rebuild to get money out of it. I'm pretty sure I'm going to rebuild it from the ground up in the next few months.