KDXRIDER.NET

Im finally doing it. Its hybrid time! I started riding when I was 9, on an xr70, then a 100. At 14 my dad picked up a 00 kdx200. Rode that thing for about 5 years. While looking stuff up on how to upgrade, I found out about hybrids here. Another year or so went by and I found a 97 kx125 in good shape, for the right price. At the time, I had only found one swap in this year range (on pirate4x4). Didnt seem like it was to big of a deal to do. The kx ran pretty good, so thinking "its a 125, it will blow up sooner than later. Once it does, then ill swap." Well...that was in 09 or so. At this last desert 100, the day before the race, the topend started to go. Still ran. Just not great...Figured id eather make it or not. Made both laps, but used way more fuel. Glad I have a desert tank...Well, last week the teardown began. The engine has been out of the 200 for a while now. So I just pulled the wiring, and air boot. Then on to the kx...Im about half done with putting it together already. Didnt take any pics untill today, so once I post them, Ill walk threw what I did...

Sweet. Definitely show us what you did as we love seeing these builds.

Heres a teaser...

Cool. Good luck on the project.

The Desert 100 will do that to bikes, even new ones lol

And your body...lol

Before I even loosened a bolt, I ordered a muffler for a 97 kx250. (Thanks for the tip) Bolted right to the subframe, and the kdx pipe slips right on. Then came the teardown of the kx.
As others have said to do, I started engine fitment with the swingarm. Before pulling the 125, I looked at countershaft to swingarm pivot relation so I could match it up. I used the stock, lower motor mounts to center the 200. On this year kx, they are two piece, so I cut the inner section out so the 200 would slide in between. Then, I scribed where the engine was sitting on the swingarm. I cut the swingarm enough that the engine just fit. "Well, what about the spacers?" I'm glad you asked. With this year, the clutch side of the swingarm doesn't have much "extra" so I figured I'd bring it in slow. After clearancing for the spacers, I cut them down to fit, making sure of square.

After fitting the swingarm, I let the engine sit as low as it could, as others have said. There where several things I didn't like. The sprocket sat to low, the right side of the engine was about sitting on the frame, the lower mounts would be way smaller than I wanted to mess with, and of course the pipe was still a good inch or better to short. I know some of that isn't that big of a deal, but it was adding up. At that point, I remembered someone saying something about one of the stock head stays working. In this case, the kx brackets bolted right on, (had to space the clutch side out a little to match the head) and brought the sprocket into alignment. Note: didn't mention before, but you still have to drill the case, and cut the rear head stay off the head. The above pic of the sprocket is the 200 at this point. I was just showing where the kx was sitting. Now was the time to figure out pipe fitment, and motor mounts.

Get the countershaft alignment right first and the rest becomes much easier. The easiesway is to mount the engie with just the swingarm bolt, and then play with the forward head mount until the pipe is where you want it. At that point fab up your motor mounts. It's all very close since the KDX engine is a variant of the early 90s KX125. You don't need the rear head stays (I've been running my Hybrid for 11 years hard and no indications of any issues using just the front stay). The hybrid build process is really pretty painless, sure makes me wish Kawasaki would pull their collective head out and get back in the 2T game.

What bufftester said is pretty much what I was doing, but no matter how far I rocked the engine, the pipe was still about an inch out. I could have just extended it, but I didn't want to. Im sure some of you have already spotted what route I took.
And yes, it would be nice if they came out with some new 2T action.

(Keep in mind, Im about a week ahead with the actual work at this point.) Liking where the engine was sitting with the kx head stay, I started messing around with the pipe, carb, and tank. You know...just to see. Tank needs the usual heat/bend. The carb, Ill get to when I actually get that far...Like I said in my last post, I didn't want to lengthen the front of the pipe. (Might be a good idea for others though.) As I thought about it for a day, this is what I came up with...

Even though this bike has been in a sad state for years, it pained me to cut it up. Couldn't even do it in the day...went out with a flashlight, and hacksaw, and cut a little back from the motor mount. Ground the welds up top the next day...

Likely the difference in pipe fitment is likely frame related. Most Hybrids I have seen are 99 and later frames (L gen vs K gen). Coupled with differences between the 200 and 220 cylinders and stock vs aftermarket pipes probably accounts for it. A 1" extension on the pipe would hurt your top end performance a bit, but you could probably work around it with some porting work.

Just so I don't get banned right off the bat, and because I don't like looking at it, here's a pic of how it sits as I type...Ill explain/show pics from cutting the kxd, to this point.

bufftester wrote: ↑10:24 pm May 04 2023 Likely the difference in pipe fitment is likely frame related. Most Hybrids I have seen are 99 and later frames (L gen vs K gen). Coupled with differences between the 200 and 220 cylinders and stock vs aftermarket pipes probably accounts for it. A 1" extension on the pipe would hurt your top end performance a bit, but you could probably work around it with some porting work.

That's what I was thinking. Its a gnarly woods. As far as the frame, the 97 kx "engine compartment" is obviously to "deep". You could just see it...Porting...hmmm

Ridea200 wrote: ↑10:25 pm May 04 2023 Just so I don't get banned right off the bat...

And here I was just getting ready to swing the ban hammer! That was a close one!

SS109: Thanks for putting the hammer down...lol
So after cutting the kdx, I used the mount bolts to hold the tubes in place, to see where to cut the kx, leaving some extra. Better to have extra, that not enough...At the front, I used a cutoff wheel/sawzall combo, and ran down the tube, leaving the mounting pad section alone. It doesn't show in the pics because I hadn't taken any yet, but the kx frame starts to curve up well before the kdx, so I just split both tubes behind where there welded (also about where it starts curving) so I could bend them down to match the kdx section, now bolted in place.
I had a first happen when splitting the tubes behind the motor mount, under the site window...the grinder cought, which happens, but it actually flew out of my hands, across my "shop", about eating my face on the way by...I thank God for fast twitch reactions...

The next step was to get the down tube matched up. As mentioned, and can be seen in prior pics, there's about an inch difference between these frames. This is where I gained the pipe clearance. Split, and bend...

A note on the actual welding: The frame isn't really that thick. It reminded me of welding exhaust pipe, so if you're not confident/skilled enough, please have someone else do the welding portion. It is the structure of the bike after all.

Probably wouldn't hurt to use splines when you join the lower tubes together for more meat.

On the plus side, using the cradle like that gives you the case saver hoops as well. On my hybrid I actually cut them off the old KDX frame and welded them to my KX frame.