Re: Lehr Propoane motorized bikes
I doubt it's quiet, but it doesn't sound bad. (It's not grating on the ears.) I am surprised though. I have heard some really quiet propane engines (like the floor buffers in the supermarket). I think perhaps it's because a fixed speed engine can be tuned to run with a lot of exhaust pressure and baffling, especially with a few spare horsepower.
1" roller Dax Friction Drive and Tanaka 3300 with mods.