Even my R1 reads fast...I checked it against my GPS.
I think that all vehicles over read, but it's good to know by how much. More modern vehicles can have a 'speedo healer', but only for electronic ones.
On my Exup it has a mechanical drive...it is 20 years old this year...& I had the same problem with an erratic reading. I Removed the drive cable, cleaned & lubed it, & now it reads a more stable reading.