For the sake of interest, I went back and read a test of the RM125C and the differences between it and the B with regard to the front end assembly.
The changes made in the front end assembly were supposedly as follows:
- Triple Clamps had 3mm reduced offset to improve steering
- Different Spring rates, to allow a lower air pressure to be run
- Rubber mounted bars, which were rearset compared to the B model
Fork travel and front wheel assembly were unchanged.
Clearly, the fact that the C model front end installed on a B model would result in steering geometry changes to the bike, makes this a potential performance modification, even if the rider involved may not even have known that was indeed a consequence of fitting an RM125C front end to a B. Why else would Suzuki have done it in 1978?
I think the bottom line though in this whole affair is that the Vintage Nationals are just that - for Vintage bikes in their respective eras. Also, being National titles, there should be an increased scrutiny of the correctness of the bikes in respect to their era class. In other words, what might be deemed OK at a club round may not necessarily be OK at the Nationals.
So on the face of it, the protest was totally "in the spirit" of the competition and of course the decision reflects that.