I had two Yamaha EF2000 generators. One failed at ~1600 hours with an excessive engine oil leak. Back to the shop for 4 (!!) months for warranty repair. Still leaks. Second failed at ~1800 hrs with the same problem and currently in the shop for repair.
A Honda 2000 was purchased and is now in daily use. Both the Yamahas are going on Craigslist with problems duly noted. Good riddance!
When I asked the Yamaha service rep he said that he normally does not see such high hours on the units. Sorry! I bought a premium quality generator and paid the price because I intended to use it. I thought the excuse for the failure was POOR! I went as far as writing a registered letter to Yamaha Motorsports voicing my disappointment. It was received but never acknowledged.
ADIOS YAMAHA!