KX-250 in a KDX?

[b1dude]

We've seen guys put their KDX motors in a KX-125 frame...

Personally I like the ergo's of my KDX better than the KX offerrings.

Has anyone seen an effort at putting a KX-250 into one of our machines?

Didn't pick up anything other than fork conversions on my searches....Already been bitten by that bug :laugh:

Curious what we get from this thread...

Thanks fellas!

 

[mark_england]

im 98% finished a kdx200sr/kx125 hybrid now,, and i cant see any reason why you couldnt do it the other way round.

you'd have to space the swing arm to fit the kx motor.

reweld the engine mounts.

also you may need bigger radiators, [the kx ones are bigger then the kdx ones]

would you need a lighting coil fitted?

interesting concept tho,, you'd end up with a fierce mx engine in a soft enduro/trail frame

 

[xsnrg]

I think the KDX motor is the gem that makes the bike what it is due to the type of smooth power it puts out. The KDX chassis is now 10 yrs without a major update or weightloss. I agree with you that the old ergos work well in the tight sections, but the bike's biggest criticism still is that it needs at very least a suspension component update and crash diet to be in class with the KTM200 or GG200. I'm sure that is probably what lead Mark to put a KDX200 motor in a (more modern I am sure) 125 frame.

If you do it, let us know how it turns out. Mark, I look forward to read your hybrid ride reports.

 

[Sunny State KDX]

How difficult is the KDX/KX conversion. is there allot of welding and spacer fabricating to make it work?? I would imagine so.

 

[Green Hornet]

It has been done. Fredette does this conversion, but you must provide the KX w/o the KX(must send KDX Motor) motor and he will do the mods. Alot of fabricating from what I understand.

 

[mark_england]

i had a call from the editor of a uk magazine on tuesday, they want to do a feature on the bike when its done, so that should be fun.

i probably wont be doing a ride report as i've built the bike for a friend, so ill just ride it to ensure everything works ok and its safe then ill pass it on.

also ive never ridden a standard kdx so i dont really have anything to compare it with

there are a few pictures of it here,,
http://adrenalintrip.extreme.com/forum/viewtopic/74/103252?siteid=1&58
it has bash plate and hand guards now, and im just trying to figure out a wiring loom

 

[xsnrg]

Sweet looking bike. Like the black plastics but I'd be afraid to ride it in the bush again.

 

[mark_england]

xsnrg

know what you mean.. i brought the engine the stripped it to the bare cases and had them vapour blasted.

then rebuilt the engine with new seals and bearings, piston, rings. clutch etc.

welded new engine mounts and exhuast bracket then had the frame powder coated silver,

striped the wheels of the original DID rims and had the hubs powder coated satin black and relaced em with excel rims [18inch rear]

used a trail tech yamaha wr side stand [which i chopped up with a dremil to make it fit]

gasgas 200 fmf gnarly exhaust, kdx fmf powercore 2 tail pipe, gasgas bashplate, gasgas petrol tap [with reserve]
honda cr front fender, honda throttle, ktm hand gaurds.

machined a ring spacer so the smaller carb fitted the larger air boot
machined the swing arm down to fit the engine [aprox 8mm off on either side]
braided hoses
stainless steel allen bolts throughout the engine and frame.
machined the head to fit under the tank.and choped the head stay mounts off.
remade an alloy head stay to fit the frame and head.

new wheel, swing arm, linkage and stearing bearings.

ive tried to build it as a new bike ,, i dont think i could now bring myself to crash it into a tree lol


it could of been built simpler and cheaper tho

 

[Sunny State KDX]

Mark that is so nice. Pat yourself on the back thats a job well done. :)

 

[b1dude]

I think the KDX motor is the gem that makes the bike what it is due to the type of smooth power it puts out. The KDX chassis is now 10 yrs without a major update or weightloss. I agree with you that the old ergos work well in the tight sections, but the bike's biggest criticism still is that it needs at very least a suspension component update and crash diet to be in class with the KTM200 or GG200. I'm sure that is probably what lead Mark to put a KDX200 motor in a (more modern I am sure) 125 frame.

If you do it, let us know how it turns out. Mark, I look forward to read your hybrid ride reports.

Respectfully disagree. :think: Engine building 101. No replacement for displacement. Ridden the KX250 and YZ250 both. Not so much a tight woods thing in the so cal desert. The ergos that let you stand more are the real plus of the KDX. If only we could eeek out some more power....all over....ergo the 250 thing. Understand your take on the modern suspension....that's why we go to great lengths to update the shock and go to the KX USD forks on a KDX frame. Done that...loved it. Glad I didn't wind up riding a KX frame/ergos to get them.

Looking for more power. The desert environ can really demand it...from big sand climbs to the flat out..flats. The diff betwx a 200 and a 250 is very noticeable.

 

[djr]

KX 250 into KDX frame

Dirt Bike magazine years ago showed Ty Davis and Kelby Pepper both had KDXs with KX 250 swapped in. This is the wrong way in my opinion. KDX 220 into a KX 125 frame would be perfect.
Dale