kx250 hybrid

[03trx400]

blew the tranny in my 400 and happened to have a kx250 engine sitting around so once the rebuild kit comes for that she'll be going in. i've been looking for someone who's done this and have found a couple, i know i need a gusset kit which is also on the way but is there anything else i should plan ahead and be prepared for? i'm aware of the fabricating and welding which won't be a problem just wondering if there's anything else out there that could help. Thanks

[deathman53]

watch when mounting that motor, it can vibrate alot. Remember, its NON-counterbalanced. If you mount it wrong, it can/will end up like many cr500 250r swaps, looks cools, runs amazing, but you can't ride it too long and things break/vibrate loose.

[03trx400]

would mounting it with rubber bushings solve the problem? if not are there any other precautions that have been taken to help ease the vibrations? and also is there any way of installing a kdx 250 coil? Thanks, i'll post pics as progress is made

[audioworks04]

Rubber will help with the problem, but not solve it. I would send your crank out and have it professionally balanced, have heard of others having good luck with it.

[03trx400]

how expensive is that? i just ordered a complete wiseco rebuild kit..would prefer to be able to just drop it in and make up elsewhere for the non-balancing

[crlt250r]

I used expanding foam in the frame around the mounting points on mine. USE LOCKNUTS AND LOCKWASHERS AND LOCKTITE WHEREVER POSSIBLE. Rubber mount wherever you can for the exhaust, and an antivibe stem will work well. The CR 250 motor in mine doesn't vine any worse now than my old 310r. Also, it may be a good idea to tie a string around your adjustment screws on your carb, my 250 was spitting them out..

[crlt250r]

I used expanding foam in the frame around the mounting points on mine. USE LOCKNUTS AND LOCKWASHERS AND LOCKTITE WHEREVER POSSIBLE. Rubber mount wherever you can for the exhaust, and an antivibe stem will work well. The CR 250 motor in mine doesn't vine any worse now than my old 310r. Also, it may be a good idea to tie a string around your adjustment screws on your carb, my 250 was spitting them out..

[03trx400]

Originally posted by crlt250r
I used expanding foam in the frame around the mounting points on mine. USE LOCKNUTS AND LOCKWASHERS AND LOCKTITE WHEREVER POSSIBLE. Rubber mount wherever you can for the exhaust, and an antivibe stem will work well. The CR 250 motor in mine doesn't vine any worse now than my old 310r. Also, it may be a good idea to tie a string around your adjustment screws on your carb, my 250 was spitting them out..

hey thanks for the tips definitely going to use locknuts and washers everywhere, could you put up some pics of the foam? not quite sure how that would work, also would a forward kick conversion be possible? unless it clears the back heel guards but im assuming it wont?

[03trx400]

also, would anyone happen to know how this hybrid would stack up against an xr650 hybrid and other big bore sports such as ktm 525, raptor, renegade etc? the motor is a '99 with a full pro circuit race pipe and is getting complete wiseco rebuild

[250x_kyle]

Originally posted by 03trx400
also, would anyone happen to know how this hybrid would stack up against an xr650 hybrid and other big bore sports such as ktm 525, raptor, renegade etc? the motor is a '99 with a full pro circuit race pipe and is getting complete wiseco rebuild

as far as that goes it has a lot to do with tire size and gearing. motor work just helps to get up to speed faster.

as far as mounting goes i would spend some time making the motor mounts removeable and finding some sort of way make the mounts an anti vibration style hook up where it would bolt to the frame.

[crlt250r]

The foam is called Great Stuff. You can find it at home depot, in where caulking is. I drilled a small hole in the frame and shot it in, then welded the holes shut. I kept the back kicker, and to clear the pipe, I just cut an inch and a half of length from the kicker and welded it back together. Now its about the same length as the Banshee kicker....

[crlt250r]

1

http://i1194.photobucket.com/albums/aa378/Tater_woods/IMAG0109.jpg

[crlt250r]

Still need to get new plastics and recover my seat. Power is awesome for just being a nearly stock 250...

[crlt250r]

In the Ocala National Forest

http://i1194.photobucket.com/albums/aa378/Tater_woods/IMAG0116.jpg

[03trx400]

nice bike man! like what you've done with it looks pretty much factory and thats pretty creative with the foam sounds like a good idea but im going to send my crank to the crank shop in vt, for $60 they'll balance it and with the gusset kit it should be ok, if not can always pump it in later. do you think a kicker will clear the 400ex heel guards? i ride alot of rocky trails and would like to keep them if possible

[crlt250r]

Not really sure honestly.. you're working with a totally different frame as mine. I've heard of guys using yfz lockers on CR motors because of how they kick "out" might be something you could look into for the kz motor.

[03trx400]

where everything is at now, engine is just waiting on a balanced crank. also any suggestions on gearing?


http://i51.tinypic.com/wrl4de.jpghttp://i52.tinypic.com/33dlhdd.jpg

[crlt250r]

I'm running the stock rear for the lt250 on the rear. Think its a 38, and a 13 on the motor. The dirtbike gears are close ratio, so the current gear is a bit off.. Gotta change them out still. You may have issues with your airbox too...

[03trx400]

i removed the air box hopefully i'll be able to find something else to fit it, also not going to be able to get the crank balanced so i'll be doing the foam and do you think it would help if i tried to tie in mounts from 3 different spots on the front motor mount?

[chris grissom]

I did a factory race program a few years ago with this engine. I don't mind sharing my experience with this project. How we solved vibration, etc. I still have quite a few parts including a couple of different balance aspect cranks and even a couple of engine assemblies. and internal gear ratio options. If you are still working on this project or need some info call me after 4:00 CST at 731-642-0511. Chris Grissom

[audioworks04]

Looks like your dream just came true, a guy that has built this bike and actually race tested his build and fine tuned it, you could learn a lot here.

[03trx400]

Absolutely, Chris had a ton of info on tuning the motor to work in the frame, very helpful and it is much appreciated. Just waiting on a couple bearings for the bottom end and then the assembly will begin

[03trx400]

sorry it's taken so long, got busy and had to wait for some parts but the motor is finally together should be starting to fab it up very soon, will post pictures as progress is made

[03trx400]

motor mounted, gusset kit installed. fabbing the pipe up tomorrow, hopefully she'll be running soon

http://i44.tinypic.com/8wb2aq.jpg

[03trx400]

The pipe is all welded up, just need to cut and weld silencer, mount a radiator, electrical, intake, extend kicker, and cut some plastics

p.s. sorry for the poor quality pics once it's all done i'll get some better pictures

[711stretfighter]

Looks good! How's the radiator mounts coming?

[03trx400]

Thanks, hopefully will be starting on the mounts this week, have been looking for a larger single radiator but haven't found any luck finding one yet, has anyone seen the two halves mounted into an atv frame with any luck?

[711stretfighter]

I don't see why you couldn't mount two halves it might be better for you. I was lucky mine came with the radiator mounts and radiator already. Anyways looking at your pipe it looks like you won't have room for a radiator on that down tube where I have mine. You might have to move it to the front of the frame like a banshee or quadracer. That's why I ended up completely remaking the first part of my pipe from scratch so that it comes down right behind and between the a arms. If I didn't I'd never have room for the radiator.

[JOHNDOE83]

I got kinda lucky that I really only use mine for drag racing and was going with a smaller radiator, If I were gonna use a bigger one Id have a crazy time trying to find a decent spot to mount it, I did try to use the stock CR radiator but it was too big and the hoses would have run right into my pipe.

I like the two half's radiator idea, they could mount under the front fenders kinda llike air scoops.

Looks like were all gonna be done with our 2 stroke EX hybrid's around the same time :D

[03trx400]

I'm currently waiting on an old KTM radiator, but if that doesnt work i guess the kx one will go in cause i'm tired of looking at it lol, and i think there's going to be room behind the shocks inside the frame, probably where you mentioned the lt and banshee but i'm not familiar with either of those.

And JOHNDOE I really hope so, these things are gonna be sick, hoping to mx it a little bit this summer

[03trx400]

Hey, sorry to all who have followed, just returned from school in Georgia and got the quad running, it's by no means anywhere close to done but it can be ridden now. For the most part it runs good but doesn't want to idle smoothly and it actually vibrated the clutch and front brake levers off today, other than that it's a blast to ride