New Yamaha 25 Shakes

[ggray]

Just replaced an ETEC 25 with a new Yamaha F25LWTC.

I've only run it maybe 2 hours, but I'm surprised at how much it shakes...or vibrates... especially 1200 to 2500 rpms. Smooths out somewhat as speed increases, but it's still there. It can make your teeth rattle, and something rattles within or around the engine (I assume that whatever it is can be found and secured).

But I must say I'm disappointed.

Dealer says he'll take a look, but says a two cylinder won't be as smooth as a 3 cylinder. Of course, but the ETEC 25 was two cylinders, and smooth as silk. No comparison.

Anyone here have one of these two cylinder Yamaha 25 four strokes that can comment on their experience?

 

[ggray]

I still hope to hear from others who might have knowledge about this model Yamaha, but a thought has come to me.

My comparison of this two cylinder 4 stroke has been two cylinder 2 strokes motors, and I suspect that could make a difference.in the potential to shake.

It looks like both throws of the 4 stroke crankshaft are aligned together. The throws of the 2 stroke crankshaft are 180* opposed to each other, which I would think is better dynamically balanced, as well as having power pulses more evenly "distributed" around the rotation of the crankshaft. Two pulses per revolution vs. one per revolution with the 4 stroke.

So to those with any make two cylinder 4 stroke, how smooth running are they? Can you relate to a similar 2 stroke?

 

[boscoe99]

Nature of the beast.

Remember, a four stroke is firing only half as often as is a two stroke. More powerful strokes at that.

Twice as many less powerful strokes will be somewhat smoother running.

 

[ggray]

That's what I'm thinking.