Yamaha 125 Breeze won't turn over

Hello all: My wife has a 125 Breeze that was running great. Turned it off for about an hour and when she went to start it had a problem. The battery is strong and the ignition is working but all that happens when it should turn over is a Whhrrrring sound. (sorry for the noise example) It sounds like the starter is not engaging. Any help as what to look at first would be appreciated.