'99 CR250 hybrid?

KarlP · Post by **KarlP** » 01:52 pm Jun 18 2007

I picked up a CR rolling chassis. Everything appears to be there and in decent shape.

I have a "spare" KDX motor that needs a crank rebuild.

Things look like they'll fit, sort of

What do y'all think? Was that a good handling frame?

Post by **Indawoods** » 02:14 pm Jun 18 2007

Give 'er a go!

Post by **fuzzy** » 04:51 pm Jun 18 2007

That would make a nice hybrid. I've thought about building a 250-sized one. My '93 doesn't fit me, doesn't really get ridden, and I couldn't get much for it so I'd steal it's motor. Now I just gotta find a KX250 rolling chassis.

2001kdx · Post by **2001kdx** » 02:19 pm Jun 19 2007

'99 Cr250's were the third and final year of honda's first-generation aluminum frame. It was criticized for being too stiff feeling. I can only assume it would feel great to a kdx rider though....

Post by **fuzzy** » 02:56 pm Jun 19 2007

Along w/ the great susp....

KarlP · Post by **KarlP** » 03:55 pm Jun 19 2007

Stiff is better, no?

We'll have to see how it goes. The aluminum frame presents more challenges than the steel one, that's for sure.

I've always liked Honda suspension. For what it was, my old XR400 had some good suspension.

When REALLY pushed, I swear I can feel the KDX flex, I think, maybe, sort of, something happens....

Post by **fuzzy** » 04:23 pm Jun 19 2007

That will make your XR400 susp feel like your on a 70's vintage bike.

2001kdx · Post by **2001kdx** » 04:47 pm Jun 19 2007

KarlP wrote:Stiff is better, no?
.

Vibration. that bike is known for transmitting a lot of virbation. I'm sure that is what MX riders say, not KDX riders. It will be a GREAT frame to house a KDX.

KarlP · Post by **KarlP** » 08:26 am Jun 29 2007

Interesting swingarm bearing arrangement on the CR.

There are thrust bearings on both sides, outboard.

The KDX does not have those. I looked again at the KDX design and realize that it is metal to metal resisting side loads on the swingarm.
It goes frame-seal-bearing inner sleeve-seal-motor- seal-bearing inner sleeve-seal- frame
The swingarm bolt pulls it all together. The seals have metal collars built into them that maintain the spacing. As the swingarm moves up and down I assume the seals rotate in the swingarm seal pockets. The collars in the seals bear against the needle bearing ends, resisting side loads.

On the cr swingarm to KDX motor joint, it looks like I'll have to shorten one of the CR inner sleaves by 6 mm and shorten the motor mounting hole by 4 mm. The motor mounting hole will have to be drilled out to 17 mm.

I've sat the motor in the frame and it certainly looks like it will work. I'll have to make mounting brackets, of course.

Post by **fuzzy** » 11:54 am Jul 09 2007

If you search on here a bit someone a few years ago built one just like that....Then I think we never heard from him again...LOL.

KarlP · Post by **KarlP** » 12:57 pm Jul 09 2007

You think maybe he is out riding?

Or.....

The motor is clearanced (Grind on parts 'till they clear each other), the motor is in the frame, swingarm works out fine.
I used a '96 CR exhaust and cut off the part that goes in the cylinder on one of my OEM KDX pipes and welded it to the CR pipe.
Head stay worked out fine.
I've got two other motor mounts to make and sort out the radiator hoses. Flow is up the cylinder from the pump and out the head, yeah?
All the cables work.
need a set of footpegs, or LH one only, and a set of linkage bearings.
Wiring harness off the donor KDX.

I'm thinking of a green and red color scheme, just to piss people off.

Christmasy, ya know..

m0rie · Post by **m0rie** » 01:17 pm Jul 09 2007

Cool! Pictures!!!!

Motodeficient · Post by **Motodeficient** » 07:58 pm Jul 09 2007

I saw a CR250 on ebay with the KDX engine, so it is possible.... Don't remember what year CR it was.

2001kdx · Post by **2001kdx** » 08:59 pm Jul 09 2007

It was a '95. Saw it a while back. That was before the aluminum frame.

I've always liked the look of the perimeter styler frames honda has been using since 1997. Your KDX will look WILd inside that CR frame. Good luck and for god's sake, upload a picture of your progress

KarlP · Post by **KarlP** » 04:15 pm Jul 12 2007

I'll get some pictures shortly. Actually, I'll have to e-mail them to a fellow friendly board member. Our company web blocking software is pretty tight. I bet my Boss is watching right now!

The bike is coming together. I've got the motor mounted but have a LOT of frame work to do-Brakes, suspension linkage, wiring, controls etc.
The motor needs to gone through... I'm going to send the whole motor less cylinder and head off to Fredette for a crankshaft replacement unless soeone has a better idea. I'm planning to go back stock with the motor while working out the suspension and control details before upgrading the motor.

I rolled it around the garage and boy does it feel light and stiff!

m0rie · Post by **m0rie** » 05:26 pm Jul 12 2007

How does the CR250 chassis compare size-wise to the KDX chassis?

KarlP · Post by **KarlP** » 11:24 am Jul 13 2007

Seat height from ground, foot peg to seat and footpeg to handlebar all measure very similar, within an inch.
Wheelbase is about 2 inches longer. I don't know about rake.

The KDX motor is smaller than the CR motor, I'd say, but the cylinder comes out of the transmission at a bit of a forward angle. The cylinder exhaust port ended up being two inches back from the stock CR position. I had to cut two inches off an OEM KDX pipe and weld it to the stock CR pipe.

The intake worked out fine using the complete KDX airbox.

Sitting on the bike it feels completely different from the KDX. Very slim and light.

IdahoCharley · Post by **IdahoCharley** » 01:49 pm Jul 13 2007

KarlP wrote: The cylinder exhaust port ended up being two inches back from the stock CR position. I had to cut two inches off an OEM KDX pipe and weld it to the stock CR pipe.

Be interesting to see what the heck this does to the power band - i.e. the two inches and a pipe originally designed for a CR.

Got to give you and other hybrid creators credit. It is interesting to watch and see the final outcomes. Don't believe it is fair to Penton, Burelson, Smith and others to directly compare your efforts

:: BUT creating hybrids is what ultimately lead to the development of a number of new models of dirt bikes.

KarlP · Post by **KarlP** » 04:32 pm Jul 13 2007

I'm no Penton, that's for sure.

All I'm doing is screwing around- putting a low power motor in a high power frame. I've ridden a number of CR's over the years and found them way to powerfull for woods riding.

On the pipe-
I added two inches to the straight part of the CR250 pipe, before expansion starts. It needed some of that, comparing to the KDX stock pipe. The expansion area is larger on the CR pipe, but I had to dent it to clear the right side of the radiator and also the KIPS shaft cover.
I have no idea what it will do, but I bet it will be different than the stock KDX pipe.

My plan is to go ahead with a stock motor and work out the suspension and ergonomics (?) before considering doing any motor work.

My recent experience with my plugged up stock SA has further convinced me that speed is in the frame/suspension first, motor second to a large extent.

KarlP · Post by **KarlP** » 03:52 pm Aug 23 2007

Just an update-

The motor is on the way back from Mr. Fredette.
(spent way more than I wanted to, but heck, that's why I have a job)

Assembly begins!

If someone will send me an e-mail adress and is willing to post pictures, I'll take some.

KDXRIDER.NET

KDXRIDER.NET

'99 CR250 hybrid?

'99 CR250 hybrid?