i need some info on installing a radr detector on my bike!

You can run it to the fuse box since the bike is also 12 volts. You want to have it fuse protected, though, or you risk damage and fire.

Chances are the original plug has a fuse inside it. You may want to use one of that rating near the unit for circuitry protection, and use one of higher ampacity at the source simply to prevent fire in the wire. That's the way some cell phone hands-free kits are set up.

Radio Shack has fuses with leads coming directly off them for expansion purposes, and you may find piggyback devices which allow a second fuse from a single panel socket, with the first fuse protecting the original circuit, and the second one protecting the expansion lead. You could put in a 5+ amp fuse at the panel, and a lower rated one inline near the detector. Double protection.