The French built race bikes have all kinds of internal case modifications. My nephew has one of them, from the North American '06 WEC rounds, and we have yet to have to tear it down for anything other than a couple top ends.
At one point we thought we had to convert it to a 250 for a weekend (we were out of 300 pistons) and we discoverd that the cylinders would not swap out due to the case modifications.
One of these days we'll get around to it and document some of the changes.
They mostly modify the case volume and flow characteristics yet still keep compression about the same as the bike he has never really needs race gas other than good fresh premium pump gas.
They also remap the CDI and block off the small compression relief hole, found on the PV side of cylinder that helps lower compression for starting, to raise compression slightly at lower rpms.
Power delivery on that 300 motor is sweet. Hasslebri was the original US owner where he had it for a year and has dibs on it if it ever comes up for sale again. Hopefully I can beat him to it
