Is there a book or site that will tell the differences between models? I like to know everything I can about my bikes. For example, I just picked up a '92 FXRS and would like to know the difference between it, and the FXR. I know on the first "S" it meant sport. Dual disc, air forks, and I don't know what else. I'm 99 1/2% sure this bike is an all original bike, but it don't have dual disc and it don't have an aire front end. The numbers say it's an "S".