1999 KX125/KDX220 hybrid

Discussion for swapping a KDX motor in a MX frame...
Post Reply
jfmock
Member
Posts: 2
Joined: 09:46 am Jun 22 2011
Country:

1999 KX125/KDX220 hybrid

Post by jfmock »

Ok, so here is the deal, I have a 1999 KX125 that does not run anymore. Needs more motor work than I think it's worth. After doing alot of reading, I'm interested in doing one of these hybrids with a KDX220 motor. I have read as many threads here as I can and still have a few questions. I'm semi mechanically inclined. Swapping motors, fabricating motor mounts and trimming/modifying are things I am capable of doing.

Right now my biggest question is what year or range of years KDX220 motor should I be looking for that will be the easiest fit into my KX125 frame? Also looking for any suggestions on where to find such a motor. I have scoured ebay and craigslists along with google searches. Seem to only be able to find mid 1980's motors. I don't think I would want to use a motor quite that old.

Next question is about exhaust and carburetor. Would my existing KX125 exhaust and carburetor work with a KDX220 motor? Or would I need to get matching parts for the KDX220. That wouldn't be a problem, it would just add cost to my project.

I appreciate any input you guys may have. I'm glad i stumbled on this site here. Lot's of useful information :D
User avatar
SS109
KDXRider.net
KDXRider.net
Posts: 5770
Joined: 05:11 am Aug 23 2009
Country: USA
Location: Tucson, AZ, USA
Contact:

Post by SS109 »

As far as KDX220 engines go they are all the same. Just get the nicest one you can find that fits your budget. BTW, to get it you will probably end up buying a complete bike.

Hopefully some others will be along here to fill you in on more details.
Youtube Channel: WildAzzRacing
AZ State Parks & Trails OHV Ambassador - Trail Riders of Southern AZ
Current KDX: '98 KDX220
Old KDX: '90 KDX200 -White/Blue
'11 GasGas EC250R
User avatar
Tedh98
Supporting Member II
Supporting Member II
Posts: 1576
Joined: 01:08 pm Mar 20 2009
Country:
Location: Atlanta, Georgia
Contact:

Re: 1999 KX125/KDX220 hybrid

Post by Tedh98 »

>|<>QBB<
jfmock wrote:Next question is about exhaust and carburetor. Would my existing KX125 exhaust and carburetor work with a KDX220 motor? Or would I need to get matching parts for the KDX220. That wouldn't be a problem, it would just add cost to my project.
The motor would run the best with a KDX pipe and carb (you also need the electronics from a KDX). You can probably get it to run with the 125 parts, but it won't run well. Plus you'll have spent a lot of time doing it.


As was mentioned, to get a KDX motor, you'll probably be buying a complete bike. It isn't easy finding just a motor.
dfeckel
Platinum Member
Platinum Member
Posts: 644
Joined: 07:46 am Nov 09 2009
Country:

Post by dfeckel »

ARe you opposed to looking for a 200 motor? If not, there were two on eBay recently in the $600 neighborhood. In terms of good years for motors, you should stick to 1995 and later (H series). The '89-'94 motors (E series) have a powervalve design that tends not to be very reliable. They're still reliable motors, as a broken powervalve will not strand you on the trail, but it's annoying to have to replace one or two of the valves annually. Plus, a KDX performance pipe that will fit your chassis will fit the H series motors a lot better than the E series motors, and they wont need nearly as much modification to fit.

Another difference with the E and H series motors is the headstay. The E has just a rear headstay mount, and the H has front and rear. I've seen builds where one or the other headstay isn't used on the H, and the other needed to be cut off the head to make fuel tank clearance. I think your 1999 125 has a front stay, so you probably will have to remove the rear mount from the KDX head. Not a big dean, just some careful sawzall cuts and a little die grinder action.

I do think that buying a whole bike will be an easier proposition than getting the necessary parts a la cart. It'll have the correct ignition, the carb, throttle with cable, clutch cable with lever, radiator hoses in the right configuration, correct clamp for the airbox boot-to-carb junction (you need the smaller KDX clamp to squeeze the larger KX boot down far enough to seal on the carb), the KDX is likely to already have a usable exhaust, all the right motor mount bolts, and various other useful fasteners and pipe mounts and such. Then whatever KDX chassis parts you have left over you can sell to make some money back. I think you'll probably end up spending less money just buying a used up KDX donor bike.

Good hunting!
David Eckel
jfmock
Member
Posts: 2
Joined: 09:46 am Jun 22 2011
Country:

Post by jfmock »

Cool, thanks for the information. I'm not opposed to a 200, just partial to a 220. I use to have a 99 KDX220 and know how boss they are. I'm sure there is probably not a noticeable difference between 200 and 220.

Thanks for the information, I'm going to keep my eyes open for a solid running bike for cheap. I figured I needed more than just the motor
SAPPER
Member
Posts: 52
Joined: 08:47 pm Dec 30 2009
Country:

Post by SAPPER »

here ya go:

http://cgi.ebay.com/ebaymotors/1995-200 ... ccessories

http://cgi.ebay.com/ebaymotors/1995-200 ... ccessories

looks like all youll need is the carb/air box boot and the radiators
real men measure with inches not centimeters

kx125 mine
kx250 dads
kx65 sisters
lt-z250 moms
Post Reply