Helmet Lock Problems

This is going to be a simple generic post
I have a 1981 KZ 1100 shaft drive that I recently just bought with a helmet lock that is located on the right side of the bike. And my key does not seem to even fit inside of it! Is appears to be stock, generally is it the same key that goes with the ignition? Or is there a separate helmet lock key. And is there an easy way to replace the whole locking mechanism with another?

Sorry for not sufficient details, if further questions need to be asked, then ask away!

del

Spray some WD40 or similar into the keyhole and let it soak. If your key still doesn't slide in and work, maybe there's a broken key in there or something else. The key should slide in even if it's the wrong key. Shine into the keyhole with a flashlight and look for an obsruction/broken key.