I carry a firearm pretty much everywhere I go, and on the bike is no exception. Is it necessary? Probably not. But then again I've never needed my smoke detectors or fire extinguishers either, and only very rarely needed my seat belts. I'm still glad I have them all.
However, if you are planning on riding in CA and OR, neither of those states are particularly gun friendly, and neither honor any other state's CCW permits. Therefore, it is likely illegal in those states for you to carry a firearm, and it is also illegal to carry a taser apparently in CA. Pepper spray/mace seems to be legal.
No matter what option you choose, the best defense of your person is situational awareness and not being oblivious to what is around you.
Enjoy your ride!