WHAT???????? Change to 18
The PO of my KTM690 went from stock wheel diameters of 21 (front) 18 (rear) to 19 (front) and 17 (rear). Did he go in the WRONG direction??????????
I don't think so. The 690's a really tall bike to start with; smaller-diameter wheels lower the bike yet keep the excellent OEM suspension characteristics.
Don't know why Kawasaki chose 17-inch rear rims. KLR650s are pretty tall bikes, themselves; Japanese, demographically, might not be as tall on average as other populations. Maybe the 17-inch rear rim fit Kawasaki's seat height design goal more conveniently than an 18-inch would.
That said, unless you're riding alone in somewhere of mostly-unavaiable re-supply (for example, Lower SlobBovia), suitable 17" rear casings for the KLR650 seem reasonably attainable.
I'd hope replacement tires are available on inmates' rides; I'm not a fan of the Jed Clampett Beverley Hillbillies style of spare casings lashed to the vehicle. But, I've never been in a situation where I NEEDED a ride-along spare tire; YMMV!
By the way; changing wheel sizes is VERY (un-KLRista characteristically) EXPENSIVE!!!!!!!!!!!!! Bring money, if you want to implant a different-sized wheel.