>Same goes for Harley Davidsons vs regular motorbikes.

With Harley-Davidson motorcycles, the V-Twin cylinders are 45° apart. With most other V-Twin makes the cylinders are 90° apart. The cylinders fire at slightly different times relative to the other cylinder and produces a different sound.

And, of course, a V-Twin will sound different than other engine configurations like an inline four or a triple.

A Boss Hoss sounds like a small block Chevy because it has a small block Chevy engine in it. For example, https://bosshoss.com/motorbike/standard-bike/