There is something specifically about a Sportster that does something for me. Harley guys are the quintessential "bad boys" too, and put them together with a little P pad seat and look out. They call them Milwaukee Vibrators for a reason, something to do with the way the large unbalanced engine is directly bolted into the frame or something. I have fond memories of those times, and your story brought me back there for a bit, so thank you for that.
The story about how Roxy got introduced to bondage is hot as well, and I could also see a testosterone pumped teen guy doing that to his annoying sister, without there being a direct sexual component to the act. They grew up together, so they'd probably seen each other in their skin accidentally a few times; in and out of the shower, rushing to get ready for school, ect... so maybe no big deal to them.
Anyway, thank you again for sharing, Jackie.