Hi Ron, I have only seen one body with that bleed hole and machining and thought it had been machined by some clever enthusiast. Interesting what can be found in UK if you go looking. I will be on a mission now to check the Matchless motorbikes that I know off to see if they have that drilling.
Robb a 276/400R was fitted to a WD Matchless G3, and originally was fitted with a 276B/1J. The 276/400R is a body supplied to replace the worn out 276B/1J, It has a one inch choke so same as a BSA M20 carb body.
I used to get a lot of guys ring me with a list of a dozen or so carb numbers that they wanted to know what they fitted so they could sell them quicker at Swapmeets (Autojumbles) as unless they wrote it on most guys did not know what carb they were chasing for their project.
