Modern Vespa

Is there much difference between a rotary-valve engine a piston-ported one when it comes to how they sound?

Is it a subtle difference? I've read comments where people say there is not much difference…

Unfortunately, I can't compare. I run a rotary-valve engine on a piston-ported Vespa. Is there a way to make them sound similar?

yes there is a different sound.

no you cannot recreate it.

to the untrained ear or unless you heard them side by side very few would be the wiser.

Most piston ported intakes are now reed valve, as piston ported without a reed valve are only good for low power setups. Whereas piston ported with reeds are the highest power setups.

What you are probably hearing is the reed valve. Which can be fitted to your rotary and would sound very similar.

Does this mean I can upgrade my 58VNA piston ported engine to a Reed set up?

I love the sounds a Vespa makes. The whine of straight cut gears being one of my favorites. I think it's more pronounced on the older large frames. Kind of like the Jetson's car.

Correct me if I'm wrong, but with a reed valve on a crank inducted motor, the vacuum opens the valve almost as soon as the piston rises. On a piston-ported motor, the piston travels a ways up before the port is open so there's some vacuum pop when it does. I know on my SS that with the air cleaner off the intake almost seems as loud as the exhaust.

Hmmmm

On sounds… based on a brief affair with a Lambretta and a few months with my ss180. I didn't notice either intake as being particularly louder, but the sound is slightly different.


What I did notice: both felt exceptionally smooth while riding... "Like floating out on a cloud of titties"

Apparently I am building the wrong kind of motor

Yeah , that's probably wrong as there is likely some overlap with the transfer ports.

Ring a ding ding, dang a ding dang, brrraaapp pop pop.

I've never really noticed the piston port vs. rotary port sound, but the only comparison I'd have would be between my Puch and my v90, so they sound way different anyway. Reeds definitely sound different.