One way I sometimes check when I don't know is to check a part number on bikebandit for my bike, then compare it to a part number I do know. Sometimes, you can find out like that. I think Honda used pretty standard stuff on their sportbikes, but I have never looked at the one on a 1991 so I can't say for sure. You could probably find the one for a 1991 on bikebandit or servicehonda.com, though. Just not sure about the key, though.
