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.

 

[Solittle]

Re: Yamaha Harmonics problem

What you have is a harmonic vibration but I have no clue to the cause. I would keep clear of that rpm range. Harmonic vibrations are what caused the loss of several Lockheed Electra turbo prop airplanes many years ago. The vibration tor the engines off of the wings.