KX250 wheels on KX500

See if the bearings cross reference.. that will at least tell you axle sizes are same or different..

Don’t know if you have ever been on kxriders or Sandblasters https://oem-cycle.com/forum/index.php
Some good info there even though most of the people went over to Facebook instead of sticking to the forum. At one time there was some good stuff, but then it went a bit sideways.

If the inner spacer, bearings and outer spacers are the same, well, that part of it seems sorted.

Though, the positioning on both the Disc and the Sprocket on the actual Hub are a Big factor in it all being viable.

I've used a spare 1989 CR rear wheel on my 2002 CRE500 to have easy tyre selection. Though, since that had only 1 bearing on the drive side (that carks it even with a 125 / 250 4t power plant), I fitted a non OEM Double row bearing to that side. I then had to make a new axle spacer to bring it all back to the same overall width as the OEM wheel. Later, when I fitted a 240mm CR250 disc and carrier ( I think from a 2001 250?) , I had to make a press in spacer to both reduce the ID of the carrier at the axle, and add 'to hub / bearing side' width to it. Almost anything can be done, with a bit of work, and tooling / machining.

I'm more a KX125/250 guy but the 02 was before any rear axle change/major chassis change. It should fit no prob. 03+ and pre 02 are different with the 125/250's.

Honestly I have never tried or looked into it. If it was me, I’d research the above links or if you have Facebook check out the KX Guru page. I believe a lot of the Kxriders members joined there and still have some good knowledge floating around. Mike from Oem is a true diehard along with some others that have done extensive R&D on keeping the 500 alive.