Hi, Andy. Welcome to the R65 Asylum... once interned, there ain't no escape.
A couple other ideas for you:
Consider flushing out the fuel tank and doing a close examination for potential rust and/or flaking of any tank liner material. The carb float bowls are likely in poor shape due to fuel deposits left by evaporating fuel. Could be a clogged fuel/air orifice, damaged diaphrams, clogged jets, blah, blah, blah.
Research the site for carb overhaul info and do only one at a time so you'll have a reference when the senior moments strike. The enrichener units, plus the Bing main carb body, have "handed" components; ie: left-side only and right-side only.
Are you running the old, metal-covered spark plug caps? Status of plug leads and coil/s? Corroded wire connections can play havoc with proper running.
A good manual is very helpful. Lots to do.
Monte