I have been thinking about this and while I know how and when it was first spelled, I also concede that as some have stated so eloquently, we have invented a new word. It's obvious that "minibike" is "now" one word for all practical purposes.
We never said "mini cycle" or even "minicycle" when they came out. We said "80." (Hey, let's go ride the 80!) The terms mini cycle and midi cycle and overall adjectivation has been occurring since the "dumbing down" began which is about the same time as shop classes and Civics disappeared from our public schools. We can thank our advertisers, and our laziness.
Since everyone on the planet now seems to own a fancy cell phone and does "texts," imagine what some of our etymology is going to look like in fifty more years! Pfft. And we bitched about "ebonics." :laugh: