Yamaha Harmonics problem

[Charlie Swann]

I just did a rebuild on a '90 Yamaha ProV 150, putting in two new pistons. Engine failure appeared to be from carbon buildup at the rings (Pennzoil if you're wondering). It runs beautifully, but sings loudly from 37-3900 rpms. It is quiet everywhere else. I feel if it were a bearing, it would get louder with more rpm's, but it goes silent above 3900. I'm stumped.

 

[Forktail]

Re: Yamaha Harmonics problem

That's why I would've put in all 6 balanced pistons.

 

[moderator1]

Re: Yamaha Harmonics problem

Moving to Yamaha Repair Questions.