Steel frame engine fitment (03-04 KX250 2t)

[The Flyin Hawaiian]

I have my 500 engine sitting in my 04 250 frame and have a few questions. Those that have done the 99-02 conversion, can a top end job be done with the engine in the frame? My head stay is mounted in the back, but it looks too close to the cylinder, its actually hitting the head stay on the head. I havent cut the front frame mounts yet, it looks like with them removed I may have the room to remove the topend w/o removing the engine. Any opinions would be greatly appreciated.
Some pics.

[BDI]

On my 02 kx250/500 I have to remove the two front head studs to get the jug off. It's a minor inconvenience but yes the top end can be done in the frame, atleast with my 02 it can.

[doordie]

Put in helicoil(steel) threads in the two fronthead holes and use a bolt instead for stock studs,otherwise you were out aluminiumthreads in barell when you have to
do a topend.

[doordie]

KX250/500-03 hybrid solutions.

[The Flyin Hawaiian]

Thanks alot Doordie!

[doordie]

Thanks alot Doordie!

No problem! 

[KXer]

I know you found your answer, but I also found that I had to remove the front (2) head studs to get the cylinder to fit (while in the frame) with the bottom end already mounted.

Tight fit, but it fits.

[The Flyin Hawaiian]

I was going to leave it and just pull the motor when its top end time but I think Im going to remove the studs also. Im just waiting for some extra cash to get the few parts that I need. Hopefully soon.

[The Flyin Hawaiian]

Some updated pics of my progress. I got a chance to work on it some last night. I got impatient and didnt feel like waiting for my friend to do the machine work to the swing arm so I decided to give it a try my self. It went well and was a lot easier than I had thought. I cut the swing arm and the spacers, very carefully, with a cut off wheel. A little filing and the whole back half was on the bike. I did have my friend cut and re drill  the head stay shorter on the head to clear the frame stay. I am going to try to use the stock 04 250 rads but I may have to space them upwards a little to clear the cyl and head. I also have to figure out the airboot to airbox mounting. So far, I am using the 500 airboot. I tried to use the stock 500 intake manifold but it put the carb too close to the shock. I ended up using the intake off of my 04 250, which angles the carb away from the shock and more or less centers the intake side of the carb between the shock and frame, gaining much needed clearance. I will use a V Force 2 from my 03 250.
Swing arm mounted

Tank clearance, no mods needed to tank, IMS or Clarke will not fit at all!

Cut and redrilled head.

Carb with 04 KX250 intake, will use a 03 250 intake with a V Force 2, this was only for fitment purposes. Cant see much in this pic.


If anybody has any suggestions, please let me know.
Rob

[PowerFiend]

How far off was the large clarke tank?

[PowerFiend]

Also, did you happen to measure how much taller the 500 sits in the frame than the 250?

thanks.

[The Flyin Hawaiian]

The tank will need an extreme amount of modification to fit, way more than what a heat gun can do. It seems that the guys doing the AF conversions have alot less work to do to the tanks to get them to fit. If I can find a large capacity tank from a 450F, Id like to see if that tank will have more clearance. A friend of mine used to make carbon fiber tanks for Team Yamaha Offroad, he also made the A-Loop CR styled XR400 tank and did some developement work for IMS. I may ask him if he would want to do a tank for me. I know it will be expensive though! I didnt get to measure the height between the 250 and 500 but I have another 250 that I can get a measurement from.

[PowerFiend]

Well that's a bummer. I already have a 2003 KX125 rolling chassis that I had started to mod for a KDX220 motor, I even clearanced a Clarke tank for its water outlet. I figured with a new engine cradle and a bit more tank work I would be good to go for the 500 swap.

On a brighter note, I did trade the 97 KDX today for a pretty clean 01 500 and a few bones. 

[The Flyin Hawaiian]

My next project will be a 03 up 125 chassis with a 200/220 motor. how much work did you do to the tank for your project?

[PowerFiend]

My next project will be a 03 up 125 chassis with a 200/220 motor. how much work did you do to the tank for your project?

It needs to be clearanced above the water outlet on the head next to the petcock, and will need some clearancing on the right side of the rear head stay. The KDX's head stay is offset more to the right than either KX (125/250).

For the front head stay there looks to be room to drill and put some through bolt style mounts, but you will need to angle the bottom cross-overs on the rads downward slightly for clearance. For the rear head stay it is in a tunnel on the Clarke tank, so just shorten and make some appropriate angled aluminum plate headstays, possibly already done from another donor bike. They are long, but the later CR250 plates look to have the correct angled offset.