It depends on the bore size, larger bores 72 85mm have 0.08mm clearance when new.
Also Pistons are not round, they are cam ground and tapered (largest diameter at bottom)
Its best to measure the bore against the manufactures limits, not piston in bore
Why not just let the top riders use modern machines then or not score lesser riders??? Surely everybody deserves a sporting chance or what’s the point in competing!
I’ve seen the same happen in the Classic Motocross, and a lot of my friends have stopped riding for this very reason!
The problem with all these modifications is out-prices the average competitor, take for a example fiddle forks in pre65. Basically they are just cheating, and killing the sport
I have no problem with fitting spanish forks / brakes to a pre65s as long as it
