What differences make a dirt bike’s engine sound high-pitched and tinny, but something like a Harley-Davidson’s engine sound deep and rumbly?

Question

Edit: I’m referring more to those heavy cruising bikes than specifically Harleys, but it seems the engine traits are similar enough anyway.

So from what I’m getting from the answers, the reason heavy cruising bikes sound so deep compared to dirtbikes is primarily the resonance due to engine size as well as being a four-stroke design. And since the extra tinny-sounding two-strokes aren’t much of a thing anymore, it’s mostly due to engine size now. (With some influence from muffler design.)

Thanks for the answers!

In: Technology

Answer 1

First off, the high pitched and tinny dirt bike engines you’re thinking of were probably fairly small two stroke engines, while Harleys are big four stroke engines. That’s a big difference right there, but two stroke dirt bikes aren’t made anymore, so it’s one that has gone away. Modern four stroke dirt bikes have a much deeper sound than the old two stroke bikes, although the engines are still half the size of an average Harley engine or less most of the time, so they’re not as deep and loud as a typical Harley. They also have much different exhaust and rev a lot higher, so they sound different.