Seat bolt vibrated loose, and now lost.
I returned it to the dealer about a week later, because it was backfiring. I even told the mechanic; that the service book says it's more than likely a loose battery. They jacked the carburator, took two days, and said it was fixed. Lie.
So I took it to another Kawasaki dealer. It took the guy 10 minutes to fix it; now it's the carbs going dry at the wrong time.
Kawasaki EN500's fuel vent line can easily become pinched between frame and seat. After 15-20 minutes on the highway, the bike became starved for fuel. Solution: pull over, pop gas cap, wait 30 seconds, then drive home, and reroute fuel vent line. I used a cable tie and it works fine. Dealer tried to fix it but couldn't.