Actually, Service Honda offers a CR500AFX. Which is a CRF250X frame (green sticker frame) paired with a CR500R engine (grandfathered into the green sticker program) allowing it to retain its California green sticker legal status.You can't get a green sticker in California for any two stroke. Closed course competition only.
The Service company has been making these for 15yrs that I know of. They are slipping thru the cracks because of low production quantity. When 2 stroke off roaders were the norm, the few 4 strokes out there became interesting because they were in the minority. Now we see the reverse happening. Build a single cyl diesel offroader with an auto trans and you will be the king of weirdIt's not street legal, so it's not subject to on-highway emission regulations. From what I can gather, it is not actually a production Kawasaki model. There are some emission requirements for off-highway engines that the major manufacturers have to follow, but one-off and low-quantity stuff either isn't subject to those requirements, or they ARE subject to the requirements but slip through the cracks because nobody's checking up on them.