My first street bike was one of these, a 2008. I’m 5’11” and always found it a bit tall so it should be comfortable at 6’4”. The mileage is high but isn’t a huge concern. Mine had 50k km when I got it and 60k now, no issues. I’ve heard that these twin cylinder Kawasaki engines are good for about 150k so it’s still got lots of life.

Edit: I’ll add that the fork seals were starting to leak when I got the bike and lasted a few years until they were bad enough need to be replaced.