99 KDX engine swap into old E-series hybrid?

Discussion for swapping a KDX motor in a MX frame...

99 KDX engine swap into old E-series hybrid?

Postby TurboStew » 07:50 pm Jun 18 2012

I bought a 1991 KX125 frame with a grenaded 1990 KDX200 engine in it for $150. I have a 1999 KDX220 bike, what are the odds that the H-series bolt holes line up (except for the head stay)? The hybrid has a leaky rear shock and missing a radiator. I love my other KDX200H, I really want to try a hybrid, but not sure i want to disassemble my 220 for an old 1991 chassis. I am 6" and 230, but the 91 chassis seems as big as the KDX to me, and these old chassis seem comfy as well. Thoughts and opinions?

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Re: 99 KDX engine swap into old E-series hybrid?

Postby Julien D » 08:10 pm Jun 18 2012

I'd say it would probably fit. May have some pipe fitment issues, but probably nothing major.
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99 KDX engine swap into old E-series hybrid?

Postby TurboStew » 10:23 pm Jun 18 2012

Thanks Julien,
I don't care about the pipe, I can fab that, they just have a nice powercoating on the frame that I don't really want to mess up with new brackets.

Is the 91 a good chassis? I have searched on the forums quite a bit and most use the newer chassis, it seems the consensus is the 94-98 have the comfy seats (I'm 41 and overweight) and larger chassis. 91 fit this bill as well, or is the 94-98 a much better candidate? I guess I'm on the fence whether to try to score a 94-98 or spend a little money fixing up the run down 91.
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99 KDX engine swap into old E-series hybrid?

Postby marrk_us » 02:03 am Jun 19 2012

If an E series has already been in the frame then your H should bolt right in and the sprocket should line up no problem. The KIPS takes up a little more room towards the front so check your clearance. Fab a head mount, hook up the radiators and you should be in business. Here's a link to my first hybrid build (e series in 90 kx125 frame). If you revalve your suspension you'll never miss the H frame. Even a 90 kx125 frame is light years ahead of the boat anchor E and H bikes, lighter with much better suspension. Once mine was done my KDX220 with revalved shock and USD's immediately became a loaner bike and was sold shortly after that. The pipe really isn't much of a problem to fab. Here's a link to the build viewtopic.php?f=111&t=6270. I used a larger aftermarket tank and had to "mold" the bottom to clear the cylinder some, yours may need some additional tweaking with the different topend but again not a big deal.
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99 KDX engine swap into old E-series hybrid?

Postby Julien D » 06:59 am Jun 19 2012

Dang, I had forgotten how awesome that bike turned out Marrk! I gotta find a motor for this 94 125.
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99 KDX engine swap into old E-series hybrid?

Postby TurboStew » 07:37 pm Jun 19 2012

Thanks marrk_us for the good info!

I just dropped the H cylinder on the E engine and it is a no-go. As you stated, the KIPS hits the frame.....Bummer :cry: . Now I need to find a complete topend for the E as the cylinder is wasted, missing some of the KIPS parts, and rod is bent. Cheaper to buy an E bike donor. The other option is to raise the front of the H engine to pivot it away from the frame, but that would require new mounts and drive the head more into the tank. hum......

Has anyone put an H motor in an older KX125? I have searched images till I am seeing cross-eye...I can't find one.
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