Generator runs, but does not generate electricity

Question

I have a Valsi GV75MG1300TV 7500 Watt generator that I purchased and used after Hurricane Katrina. The motor still runs fine and I start it every few months, but when I needed power after Hurricane Gustav, it would not generate electricity. The Voltmeter on the Generator is not registering anything. It will occasionally bump off of zero, but not for any amount of time. I checked connections and flipped breakers, but have not gotten anything out of it. Reading the manual seems to indicate that a capicator or diode coule be broken?? I have also heard others say that sometimes generators need to be reset ot "Tickled". Please help. Thanks.