I have a 2000 watt generator from Costco with a Yamaha motor. Started it a couple of weeks ago and everything was fine. Now the dam thing won't start. Dumped the gas and started with fresh gas, but nothing. Checked to make sure that I'm getting gas at the carb, have spark, but still nothing. Will fire sometimes with starter fluid, but now always. Is there anything special on these things that I'm missing?