When you say it won't start do you mean it turns over but won't start or it won't turn over? If it turns over but doesn't start try holding down on the stop side of the switch for about 45 seconds to make sure the engine is primed then try starting. If it has been a long time since the generator was started your fuel bowl may be dry.
There is a drain plug at the bottom of the fuel bowl, after you've tried priming and it won't start, loosen the plug and make sure you are getting fuel.
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