Hi Malcolm,
thanks for your help to find the answer on this percentage issue.
My last rule information on paper is from the 76/77 season - when I tried to find Kitty O'Niel (Hamilton) and the SMI Motivator.
I remember very well, that on one of the pages with the rules was this information with the 1 % rule.
I tried to go through the current FIM rules (which I download 2 years ago) but that thing drives me crazy (if someone says now, I'm crazy.....yes...and I'm proud on this..

).
So you be in the same position as I, in the moment. In one of my 12 boxes with the archived material is somewhere this old FIM paper - but in which one.
May be I got time on the weekend to check this. Hope you be successful - for me, to drop this rule, sounds very strange and it would make no sense, especially to all this nearly record holder who couldn't set a new record due to this rule.
Mike (Akatiff) mentioned a while ago something in a note here on Landracing, which nobody understand what he liked to say in his writing. I never heard something that the FIM changed something with the percentage - but that means nothing. The FIM done so much over the last 10-15 years that everybody went confuse.
But Chris and the BUB7 was so much over the old record that there is so or so no problem - unluckily, he didn't broke the 600 kmh mark...