How do I convert kz440 wheels to work on kz650

IMHO, having a machinist make the adapter would probably be safer. I'm assuming you used steel shim stock? If so, keep in mind that it's in an aluminum wheel and the aluminum wheel is a lot softer than the shim stock.

A long time ago, when working as a mechanic for a trucking company that was on a shoestring budget, we used aluminum cut from beer cans to shim the bearings in aluminum front hubs. Never did hear of it failing, and it had 6000 lbs on each front wheel.

My local machinist won't do what you describe, he's concerned about the rider crashing for some other reason and the family sueing him, so he won't do any suspension work at all. At least that's what he said when I asked him to do the same thing for me.

well that is a conunfdrum of sorts because what I have now is that shim and bearing. It fits fine. BUT like I said, the shim is corrugated & is meant for some lateral movement. This guy I spoke to said it is meant for areas that expand & contract with heat - that is why it has a flex. The weight index says up to 1200 pounds so I guess the weight would be fine but maybe it is better to be safe than sorry... I will wait for the 20 x 42 x 12 bearings to come & then take those with the axel sleeve to the machinist & see if he can even do it...

If I was doing it, I would use 1mm flat shim stock and cut it to size. That would take up your 2mm clearance and make it a tight fit. But others on this board would take exception to this, so I seldomly mention it.
If I were to do this, I would peen over the outside of the rim where the shim is to make sure it stayed in place.