Like @Chooglin said, no reason for concern. I'm sure that Yamaha, Kawi, Suzuki, Canam, etc all recommend to periodically check valve clearances. It's just the nature of a small engine. If you don't want to deal with occasional valve adjustments, the old Polaris 700 and 800 engines have hydraulic lifters... My Night Rod Special is supposed to have the valves checked at 15,000 miles - and that is WAYYYY more of a big deal than a little Honda single cylinder.