So, the only genuine MC that are available now are the latter 13/16th ones, but no problem with that, Basil has the latter 8" front brakes anyway...
Cutting a long story short, I had the new MC in and out like a Fiddler 's elbow, well 3 times. Fortunately, one of Basil's little quirks is that when he was refurbished, they must've made their own box sections and they fitted the MC slightly higher than it should be; meaning I can easily get the Bolts in & out without messing with the Torsion bar

The problem was that I couldn't get any fluid to move from the reservoir, so was it because it needed priming or what?
Nope it wasn't that....
On the 3rd time it was out, I looked closely at the new MC, comparing it with the old one....
Is there a difference between the 7/8" and 13/16" other than the bore size...

It looked quite a bit narrower down the hole where the Operating Rod goes...
Could it be that there was something else different about it...?
. .
Boy is there ever...
Getting 2 identical length Alan Keys, I could easily see it...
. .
The original MC Operating Rod hole is close to parallel sided and 7/8" deep.
The new one is tapered to a narrow bottom but is approximately 1 & 7/16" deep, approximately half as deep again as the original item.
The problem I was having was that the Operating Rod was just going in and out of the hole and barely moving the actual Piston.
I was not going to get sufficient adjustment on the Operating Rod to take up all the slack, unless it was going to be barely on the end of the adjustment, so I took the easy way out and even with my lousy welding ability I welded a short extension to the operating rod.
I decided that all loads exerted on the rod while braking were compressive and even if the weld did separate somehow, the tapered shape of the hole would hold the end piece in place.
I'll be letting ESM know about this, perhaps it is a freak one-of, perhaps all the new ones are like it, I've no idea, but I thought I'd share the info...

