Yamaha Harmonics problem

[Charlie Swann]

Just did a rebuild on a '90 Yamaha ProV 150, replacing 2 pistons. Engine appeared to have failed from carbon buildup at rings (Pennzoil). Engine runs beautifully, but sings loudly from 37-3900 rpm's only, at all other speeds it is quiet. I feel if it were a bearing it would get louder with increased rpm's, so I'm stumped. Anyone run into this before?

 

[Canuck 16]

Re: Yamaha Harmonics problem

Charlie,<br />I would'nt worry about it. My 200 does the same thing between 36-3800. I just avoid running at those revs.<br /><br />Cheers... Canuck 16

 

[Ray Neudecker]

Re: Yamaha Harmonics problem

Most Yamahas with mechanical timing advance do have a problem with that RPM range. The timing is full advanced and the throttle is not. Not likely to be a problem, but avoiding cruising at those RPM's seems to be the only reasonable answer.