Is there a difference between a 94rr frame compared to a 98rr frame?

 

Yes, there are a couple of differences. Just a few that I know of off the top of my head:

1. The 93-95 uses 1 bolt at the top of the gas tank. The 96-99 use 2. This also relates to #2.
2. The upper fairing/mirror support bracket on the 93-95 bolts to the sides of the frame, below the gas tank. On the 96-99, it bolts on, using the 2 gas tank bolts referenced in #1.
3. There is also a difference in the triangulated area, on the sides of the frame, below the seat/tank area. I'm not sure if it makes any difference in the way things bolt up to it, though.

#'s 1 and 2 are the biggest differences that I know of.