'99 CR250 hybrid?

2001kdx · Post by **2001kdx** » 04:44 pm Aug 23 2007

I'll take care of that, plus, I wanna see your progress.

ronesadler@yahoo.com

thebleakness · Post by **thebleakness** » 04:45 pm Aug 23 2007

Awesome! Let me know how that turns out, I'm trying to figure out a way to adapt a KX250F frame with a KDX engine in it.

Take some pictures and then upload them here in the gallery, or use photobucket.com or imageshack.us.

2001kdx · Post by **2001kdx** » 05:07 pm Aug 23 2007

The handling of the MX bikes are sweet aren't they bleak?

thebleakness · Post by **thebleakness** » 05:27 pm Aug 23 2007

That and the suspension, 2 things that I think the KDX lacks. I think the new aluminum framed KX250Fs are extremely comfortable. Took some time getting used to the larger aluminum frames but once you do, wow they feel great.

KarlP · Post by **KarlP** » 07:39 am Sep 05 2007

Just a quick update-

I've sent a group of pictures to the above yahoo address.

She runs!

Fredette rebuilt the lower end, I did the upper end. Sounds tight, runs crisp.

Major set back is that I've got a crack in the CR tank, right at the petcock.
Damn

Couple of things left to do-
Finish the head stay bracket
Finish the handlebars/controls/barkbusters
mount all the ratty old plastic while deciding on the color of the new plastic
JB weld a small leak in the radiator
FIND A NEW TANK FOR A '99 CR 250

Things to do after riding a bit, if I deem it worth it-
Send the forks off for a look at; springs and valving most likely
New plastic for that COOL look
RB head and carb

Things I've done-
All new bearings in the rear suspension linkage and swingarm
Shock resprung and revalved for my weight and intended use
Motor gone through and good to go
All the gay stickers peeled off

Wish I had more time to just tinker.

2001kdx · Post by **2001kdx** » 01:22 pm Sep 05 2007

Post by **fuzzy** » 11:55 am Sep 06 2007

Looks SWEEEET! Great time for an IMS CR tank.

KarlP · Post by **KarlP** » 12:57 pm Sep 06 2007

How come I can't see those pictures?

I mean, I took them, I remember what I took, but still....

All I see are these-

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Post by **Indawoods** » 01:04 pm Sep 06 2007

That is TOOOOO cool!

m0rie · Post by **m0rie** » 01:23 pm Sep 06 2007

Looks good Karl!!! Just need a tank and your good to go!

Inda - Should this get moved into the Hybrid forum to go with the KX hybrids?

thebleakness · Post by **thebleakness** » 05:29 pm Sep 06 2007

Your doing almost exacatly what I want to do. 'Cept I want to use a KX250F frame. Too bad that front downtube isn't designed to get have a 2-stroke pipe going through it. That's going to be some interesting fabrication.

2001kdx · Post by **2001kdx** » 05:44 pm Sep 06 2007

RE: 'KX250F frame'

Hmmmm.... You must be made of money bleak, last time I checked, a KX250F rolling chassis costs A LOT more than a 125 in similar condition.... is the KXF frame really worth it? Why?

thebleakness · Post by **thebleakness** » 08:10 pm Sep 06 2007

It's been the most comfortable bike I've ever ridden. I didn't really care for the power but the ergos of it are amazing. It fits like a glove. I don't plan on doing that conversion in the near future nor do I have the money to do it but that's my dream. A dangerously modified KDX220 (maybe over bored) with everything done to in an awesome al. frame.

Post by **fuzzy** » 10:57 am Sep 07 2007

Have you ridden a 125? They should be nearly identical in the cockpit.

ebeck · Post by **ebeck** » 12:36 pm Sep 07 2007

Hey great!

The KDX rear mount on the motor is not solid. It is only a 1/2 thick sleel sleeve on either side. If you tril that down you really reduce the strength of the motor mount. I would have looked closer at modifying the swing arm more over the motor mount. Most of the swing arm is joint is just a spacer.

The Tolerance for that jont is very tight and there needs to be 2/1000 of an inch clearance between the thrust bearings and bearing surface. machining that sleeve should be done with great care.

If there is play in the swing arm it can wear out quick and casue all kinds of issues including failure of the joint.

Personally I would have a machine shop do all the work. I provided a CAD diagram of the KX swing arm.

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.

That will shift the power down a few hundred rpm. I had to use 10 extension on the KDX pipe as well on the KX hybrid.

I know a guy in Seattle who did a 99 CR250 KDX conversion as well. It appeared to be a pretty easy conversion actually. About the same as the KX/KDX. Now I see it here I would agree with that. personally, I would have made new mounts and had them welded on the CR and had a machine shop with a mill do the cutting. It is suprisingly cheap.

The swing arm joint creates a motor that is a little too loose for my tastes. I would be carfull with it at first. If the KDX motor cases crack do not blame the KDX motor.

Either way any conversion is a fun project and a KDX based motor MX bike is just incredible.

Either way the straight line stability will be awsome on the CR and the ergo's will be great.

I have seen KXF frames parted on ebay pretty cheap actually.

Welcome to the club!

KarlP · Post by **KarlP** » 12:51 pm Sep 07 2007

On welding the mounts to the frame...
I was trying not to molest the CR frame, for some reason. I got the frame for nothing. I may stumble across a running CR motor for nothing some time and want to put it in.

Any ideas on glue for a gas tank?

ebeck · Post by **ebeck** » 12:58 pm Sep 07 2007

yes there is plastic repair that auto parts stores sell. JB works well too. If it is not visible. If it is I would look to ebay KarlP.

As far as molesting the frame, yeah if you want a CR motor then what you did is best.

Hey switch motors for different days!

ebeck · Post by **ebeck** » 01:00 pm Sep 07 2007

I'd love to do that CR/KDX too.

KarlP · Post by **KarlP** » 11:22 am Sep 10 2007

Rode it around the yard a bit yesterday and Saturday.
It feels like what I expected- Light, high, and very stiff up front.

I've welded the tank and epoxied the petcock. It's holding for now, but surely not for long.

It sure does turn nice, feels like you are sitting ON the bike, driving the front wheel, rather than IN the bike riding front and rear like the KDX.

Lots of details to take care of.

KarlP · Post by **KarlP** » 02:33 pm Jan 14 2008

Its been a few months, time for an update.

I had the forks resprung and revalved and resprung. According to my suspension guy, the previous owner must have been a 300 pound supercross rider, they way it was sprung and valved.
I had the shock redone as well. Same comment as above.

It has taken quite a bit of riding to get the suspension dialed in. I've talked to dozens of people, forced many to ride it, gone from one end of the range of adjustment to the other. Finally got it over the last two weeks.

My impression is that this chassis is VERY sensitive to adjustment. Moving the forks just 2 mm in the triple clamps makes the difference between cutting too sharp or plowing through a corner. 4 clicks on an adjuster goes right past the best setting.

For now, the motor is a stock 220. I modified a '96 cr250 pipe to fit which really seems to rip in the upper RPMs, much more so than my real KDX. I don' Overall the motor performance is great!

Ergonomics and handling are where this thing shines. I've been watching my times through a couple of sections of trail and I'm picking up nearly two minutes every 12 minutes in the more open but still tight trail. In the real tight trail, the difference is less.

Nothing has broken or fallen apart. I gotta get a seat cover that doesn't say Honda.

I'm going to move my RB goodies from the KDX to the hybrid .

KDXRIDER.NET

KDXRIDER.NET

'99 CR250 hybrid?

Here they are; The bike is SWEET!