I've bought and sold cars, bikes, motorcycles, jet skis, sailboats and untold less interesting items on CL -- and never been much bothered by the scammers.
When selling, you can count on the non-sense responses (requests for VN reports and shipping). I've found putting a requirement for a cell phone number cuts that to zero.
When buying, you have to accept that a fair portion of sellers are in some type of crisis -- moving, getting divorced, life change that they didn't foresee. The bike sale may be 10% of their problem and their response is like their current life state -- kind of a cluster. I also suspect that a percentage of for sale posts are half-hearted, poorly conceived, or under the influence. Yeah, but what about the $5 fee -- seriously, when you're guided by something less than your better self, has $5 been a barrier? :laughing
It's frustrating, but try not to take it personal. And don't get desperate. People are bored right now and buying up projects they have no ability to complete. 2021 is going to be the year of cheap old motorcycles, new kayaks, and never-used portable generators.