Gasp! Horror! What will the purists think. 
I am still trying to see why it is so. At this stage I am wondering if there was ever a little "cap" that was fitted by the factory to the piston rods of master cylinders that had just a little too much free travel - 1mm of additional travel on the piston equates to quite significant amount of lever movement.
The other possibility is that in theory (according to the ever helpful guys at Motobins), the cranked lever should not fit my throttle assembly and my blade lever should not be able to be fitted to the older "round" m/c throttle assembly on my wife's bike.
I have verified that the later blade lever will not fit the 1979 R65, but I can fit either lever to my bike. Using a torch and eyeball I've had a look inside my assembly and it does look like someone has had a dremel (or similar) in there.
My working hypothesis is that sometime in the past my 1984 R65 needed a new handlebar throttle assembly and that one for an older model was sourced and then modified so that the existing blade type lever would work in it. My MPO (moronic previous owner for those that came in late) then just accepted having cr@p brakes, or alternatively, didn't know any better.
Either way, I now have a good front brake, I don't need to buy a new master cylinder and in any event I am about to fit two 4 pot calipers and will be re-sleeving an old "round" master cylinder to 17mm in honour of the twin 4-spots.
Last comment on the topic of fitting the later 4 piston calipers. Anyone who has ever looked will realize that whilst the bolting is identical to the older F08s (and earlier ATE Brembo copies) that unfortunately the centering over the disc is not.
The "traditional" way to fix this is to mill between 2.5 and 4mm from the bolt pads to correct the centering. I am confident that removing that much metal will not in any way compromise strength, but I am not entirely happy with the concept as it moves the parts into the realms of "one-off" I would prefer to leave the components in standard condition.
To that end I am designing adaptor plates that will bolt to the forklegs and which have a second plate welded to them, by milling the plates appropriately (guess who is in the process of buying a mill) I will be able to center the calipers over the discs without removing metal from the fork legs or calipers. This process will mean that the calipers will be a little further towards the outer edge of the disc but I do not see a problem with this.
As soon as I have the plates made I will provide photos and dimensions in case anyone wants to replicate them.
