I wave at everyone on motorized two-wheelers. I have done it for nearly 30 years.
Some wave back. Some are surprised (do they know about the custom?) and don't have time to do much. Some are busy or just don't want to bother, so they nod their heads.
Some riders don't wave back. Some don't see me (hopefully they are paying attention to the other aspects of their riding). Some riders see me, but don't wave back, but they never tell me why. A few scowl at me. Perhaps they don't like my bike, or waving, or are having a bad day. Is there such a thing as a bad day when you're out riding? I dunno.
Most motor officers don't wave back, but a few do.
I don't wave if it unsafe and I don't wave if the road is so populated with oncoming motorcyclists that I have to wave every few seconds or so, especially in the twisties. Sometimes a nod is good enough. I'll try to wave back or at least nod if they wave at me.
I learned last year that I have a "geek wave", which is not cool. Furthermore, geek waves are harder to do on my new bike, because the air flow is different - it can really push my hand back at higher speeds. I switched to the "two-finders-down-low" wave. It seems to work, and it isn't in the airstream, and now everyone thinks that I'm so much more cool...
...except for the orange reflector vest.