Pretty funny Peak.
Valves tighten on the KLR over time. In my experience, more at the beginning than later in mileage life. I've had them keep running with valve clearance almost nil, but they're certainly happier when they're slappy. Recent hard starting in the cold weather resolved once marginally tight valves were re-shimmed on mine.
Pretty easy job if you're mechanically inclined. Online KLR sites frequently list tech day gatherings attended by helpful experience if you want to do your own wrenching.