K5 in a 250 frame

[martinfan30]

What years should I look for? Want to put my 500 in a 250 frame. Will this actually benefit me in any way? Weight? Handling? Suspension?

[kawiscooter]

I had the same question a few weeks ago. Best bang for the buck seems to be the 99-02 chassis. There are several posts regarding this conversion.

Also, in the main topic list jfabmotorsports sells a head stay that is most helpful.

Good luck!

[PowerFiend]

I'm trying to work with an 03 KX125, which require new 250 like lower frame rails anyway. ...so save yourself time and money and stay away from 125's as starters. But hey, I got it for cheap.

Weight, not much difference.
Handling, light years better.
Suspension, also a lot better.

All cut swingarm, bore engine cases to 17mm for swingarm pivot bolt.

99-02: They are cheaper, if that is what you call bang for your buck. These require the front headstay, if I'm not mistaken.
03-04: New front motor mounts, shorten frame head stay(rear mounted), deal with lower radiator crossover(Tight fit).
05+: Should be the same as the 03-04.

Issues:
99-02, board member reported that the desert tanks require major surgery. And I believe he never got it working.
Ditto for 03-04, in fact they are probably worse. I can't see anyway without cutting and plastic welding with the clarke. In trial fitting the back two headstuds had to be removed, along with the head to even try and fit it. The tank touches the top of the cylinder on both sides, the worse being that the left side is the petcock mount.
I'm not sure about the Clarke for 05+, I haven't gotten a good look at one, but the IMS doesn't look like it will be workable. The petcock is in the wrong spot like on the 03-04.

KX250F 04-05: No one that I found offers a larger than 2.3gal tank. New frame rails, head stay, etc.
KX250F 05+: Info. is on here, but seems to be lots of work and the largest tank I found is a 2.8gal. I would go with the 450 if I was to go aluminum, since there are larger tank options.

I have a clarke I may try and butcher to work, but will probably end up adding a fork mounted .8gal to give me 3gal total with the stock tank. I need the capacity since the 500 is a thirsty girl.

[BDI]

If I was going to use a 125 frame I would get a donor 500 frame and cut the whole cradle out of the 500 and graft it to the 125 frame.

[The Flyin Hawaiian]

Ive been off for a while, had to buy a new computer! Anyhow, Im doing a 500/250 conversion using a 04 KX250 (2t) chassis. Im almost done with most of the tough stuff, its was much easier than I had thought. You can solve the fuel issue by using a 05-07 KX250 2 stroke tank. It fits with very little modification, you will have to heat the tank above the plug and fab up a new mount bracket of some sort where the Clarke tank bolts in front, it is slightly off. In 05, the 250 got a new frame that is narrower so a 03/04 tank wont fit a 05-07 frame. The 250 also got a new motor where the cylinder sits in more of a straight up position. Because of this, there is now clearance for the 500 cylinder. My fiance actualy figured this out when she was installing a Clarke tank on her 07 KX250. Before she put it on her bike, she placed it on my 250/500 project. It looks like it was made for it. If the 05-07 IMS 250 tank still uses the little side "L" brackets, you may not need to go with the Clarke. I cant confirm this though because I dont have a IMS to test fit. As far as the radiators go, im using the 250 rads. I will use the top, stock position frame mount and angle the bottom of the rads forward to clear the cylinder. The cross over is a tight fit. Im going to grind out the welded seam and have it flush welded. This should provide enough clearance. Im also going to space the rads out from the frame slightly. This should make getting to the lower crossover tube hose clamps easier. One more thing concerning the large tank, the rear frame headstay almost touches the tank where the petcock is. I dont think it will be easy to heat this area ot the tank up for claearance. So, im going to cut the frame mount out and move it to the right and line it up with the headstay. This way, spacers or offset brackets wont be needed. Hope this helps you guys out some.

[jfabmotorsports.com]

  My fiance actualy figured this out when she was installing a Clarke tank on her 07 KX250. Before she put it on her bike, she placed it on my 250/500 project. 

Never mind the project! You better hang onto her. Most of my friends women can't even tell you what brand bike they ride even if they are looking straight at it. 

[bob larry]

2nd that!  How old is the sister?

[PowerFiend]

Ive been off for a while, had to buy a new computer! Anyhow, Im doing a 500/250 conversion using a 04 KX250 (2t) chassis. Im almost done with most of the tough stuff, its was much easier than I had thought. You can solve the fuel issue by using a 05-07 KX250 2 stroke tank. It fits with very little modification, you will have to heat the tank above the plug and fab up a new mount bracket of some sort where the Clarke tank bolts in front, it is slightly off. In 05, the 250 got a new frame that is narrower so a 03/04 tank wont fit a 05-07 frame. The 250 also got a new motor where the cylinder sits in more of a straight up position. Because of this, there is now clearance for the 500 cylinder. My fiance actualy figured this out when she was installing a Clarke tank on her 07 KX250. Before she put it on her bike, she placed it on my 250/500 project. It looks like it was made for it. If the 05-07 IMS 250 tank still uses the little side "L" brackets, you may not need to go with the Clarke. I cant confirm this though because I dont have a IMS to test fit. As far as the radiators go, im using the 250 rads. I will use the top, stock position frame mount and angle the bottom of the rads forward to clear the cylinder. The cross over is a tight fit. Im going to grind out the welded seam and have it flush welded. This should provide enough clearance. Im also going to space the rads out from the frame slightly. This should make getting to the lower crossover tube hose clamps easier. One more thing concerning the large tank, the rear frame headstay almost touches the tank where the petcock is. I dont think it will be easy to heat this area ot the tank up for claearance. So, im going to cut the frame mount out and move it to the right and line it up with the headstay. This way, spacers or offset brackets wont be needed. Hope this helps you guys out some.

Most Excellent...

How much of a gap is left between the 05+ clarke and the 03-04 frame? Perhaps fill it with hot water and do the tank expansion trick??

I would go with the clarke, the IMS tanks are a nightmare to perform slight molding with. The are like trying to remold a candle with a blowtorch.

[PowerFiend]

If I was going to use a 125 frame I would get a donor 500 frame and cut the whole cradle out of the 500 and graft it to the 125 frame.

This would be way more work, the 500 frame rails flare out with the main tube to the pegs, the 125/250 flare into the linkage. The 125/250 frames also have the rails extend all the way up to the square downtube, where the 500 has that clam shell around the round downtube. ... at least on the 98 + 125/250 frames, I have not looked at anything older.

[PowerFiend]

Ive been off for a while, had to buy a new computer! Anyhow, Im doing a 500/250 conversion using a 04 KX250 (2t) chassis. Im almost done with most of the tough stuff, its was much easier than I had thought. You can solve the fuel issue by using a 05-07 KX250 2 stroke tank. It fits with very little modification, you will have to heat the tank above the plug and fab up a new mount bracket of some sort where the Clarke tank bolts in front, it is slightly off. In 05, the 250 got a new frame that is narrower so a 03/04 tank wont fit a 05-07 frame. The 250 also got a new motor where the cylinder sits in more of a straight up position. Because of this, there is now clearance for the 500 cylinder. My fiance actualy figured this out when she was installing a Clarke tank on her 07 KX250. Before she put it on her bike, she placed it on my 250/500 project. It looks like it was made for it. If the 05-07 IMS 250 tank still uses the little side "L" brackets, you may not need to go with the Clarke. I cant confirm this though because I dont have a IMS to test fit. As far as the radiators go, im using the 250 rads. I will use the top, stock position frame mount and angle the bottom of the rads forward to clear the cylinder. The cross over is a tight fit. Im going to grind out the welded seam and have it flush welded. This should provide enough clearance. Im also going to space the rads out from the frame slightly. This should make getting to the lower crossover tube hose clamps easier. One more thing concerning the large tank, the rear frame headstay almost touches the tank where the petcock is. I dont think it will be easy to heat this area ot the tank up for claearance. So, im going to cut the frame mount out and move it to the right and line it up with the headstay. This way, spacers or offset brackets wont be needed. Hope this helps you guys out some.

P.S. Any chance of some pics?

[BDI]

If I was going to use a 125 frame I would get a donor 500 frame and cut the whole cradle out of the 500 and graft it to the 125 frame.

This would be way more work, the 500 frame rails flare out with the main tube to the pegs, the 125/250 flare into the linkage. The 125/250 frames also have the rails extend all the way up to the square downtube, where the 500 has that clam shell around the round downtube. ... at least on the 98 + 125/250 frames, I have not looked at anything older.

Well that sucks and sums it up all at the same time. You just can't use a 125 frame, use a 250 and save yourself a bunch of hasle.

[The Flyin Hawaiian]

The gap is not noticeable. I think there is more room for the throttle cable, which tends to get pinched abit with the 03/04 IMS and Clarke tanks. Since the seat and plastics, with the exception of the tank, is the same between the 03/04 and the newer 05/07 KX250s, it all looks like it was made for it. I have pics but have to figure out how to load it onto my new comp. Im not very computer literate! The front of the tank, where it bolts to the upper part of the frame, is slightly off and will require a new frame mount. Its very close though.

[PowerFiend]

The gap is not noticeable. I think there is more room for the throttle cable, which tends to get pinched abit with the 03/04 IMS and Clarke tanks. Since the seat and plastics, with the exception of the tank, is the same between the 03/04 and the newer 05/07 KX250s, it all looks like it was made for it. I have pics but have to figure out how to load it onto my new comp. Im not very computer literate! The front of the tank, where it bolts to the upper part of the frame, is slightly off and will require a new frame mount. Its very close though.

Great, thanks.

PM Danger4u2 and ask for a KXRiders gallery. You can then upload to there and link those photos with the insert image icon in the response screen.