800 Motor Reliability

I'm looking at purchasing a 2013 RZR 4 800 from a local dealer. I was told by more than one person to watch out for the 800's. I've had plenty of 800's in my sleds, but this is my first ATV/UTV with the motor. Its lower miles but i don't know the history.

Are they reliable? Any issues or sounds to look out for? Anything else to be concerned about or look out for on this particular year/model?

Thanks in advance.