This has been debated a lot. The problem is, the law says if you're carrying a pistol in a motor vehicle, you need to have a CPL, otherwise, it needs to be unloaded, and as unreachable as you can make it. (I'm paraphrasing.) I know, with motorcycle, you're ON a vehicle, not in it. To be honest, I don't know if this has been tried in court.
What you need to determine, do you have the money to be a test case? Short of somehow getting an AG opinion, that is what you'd risk by OCing on motorcycle without a CPL. This is part of the reason I have a CPL.