My Brother and I bought identical Yamaha EF2000IS generators and both failed with a catastrophic oil leak at about 1500 hrs while under warranty. I took mine in to a certified Yamaha dealer for repair and waited 6 months for them to finish. When I got it back the case had been put back on and not aligned properly, the fuel shut off was almost impossible to turn, a cover was left off the connection to the electronic carb control, the weather cap on the ON/OFF switch was missing and it appeared the screws used to reassemble the case were just whatever was laying convenient on the workbench at the time. I did a test run and it still leaked oil. IMHO, it is in WORSE shape than when I took it in. I sent a certified letter to Yamaha USA and received no reply.
My brother took his generator to the same dealer since it is the only one withing a reasonable distance - and it is STILL 75 miles away. He voiced some concerns over work quality and length of stay in the shop based on my experience and yes --the service manager remembered me. The service manager flat out told him his generator would be the lowest priority of anything in the shop and he would be LUCKY to get it back in 6 months! I was absolutely astounded by the poor attitude! He asked to speak to the General Manager and was told he does not get involved with issues dealing with these "smaller units." My brother declined to leave it with that shop. He also sent a certified letter to Yamaha USA with no reply afterwards.
It is my opinion Yamaha USA has little profit margin on these generators and it is throwing bad money at them to have to do warranty service on them. As such, they basically ignore you after the sale.
I am not a complainer by nature but I made myself a promise that I would badmouth the Yamaha EF2000IS generators at every public opportunity after we had these near identical horrible experiences. When we bought the Yamahas we ***ASSUMED*** we were getting quality products while paying a premium price and would be assured of stellar warranty support. We were wrong.
FWIW, Both of us bought the Honda EU2000i generators as replacements and are well pleased. He has about 600 hrs on his and I have about 150 on mine. It is more than equal to or better than the Yamaha on most counts.