I picked up a 1997 Yamaha Big Bear 350 2X4 a week or so back in non running condition, apparently they said it needed a new carburetor or a battery, I cleaned the carburetor thoroughly and got it running on idle and without choke now and it shifts into all the gears even into reverse. Aside from making me bounce a little when trying to start out with a bit of throttle the shock suffice to say needs work. Anyways I made a video of it running and would like your opinions on it, as to how it sounds while running. It seems like it has a little whine I'm not sure why that is maybe someone can tell me what it is. Anyways here is the video.

 

I would be less worried about the whine than the clattering from the valve gear, could be the clearances need setting but it sounds more like the cam chain slack. Either way, take that big plate off the side of the head and check if the chain is tight. While it is off, move the engine round so the timing mark is nearest the "pointer" at the top, and set the valve clearances. If it needs a cam chain, this is a big job on a 350 Yam, and the balancer needs removal. This can go back on six ways and is only timed right one way, the marks are not much help either, so be sure you know how the balancer came off.