if there an air leak on the inlet side then the carb wont perform correctly as the vacuum from the engine open the power valve. have you checked for air leaks with a butane gas torch air carb clean spray.
As Andy put all accessable surfaces tested with wd40 but no leaks . You can't get to the underside of the manifold which is where the slight distortion on the head is (0.05mm)
To start with
1) Float levels reset
2) plugs removed checked +cleaned ,checked firing outside engine ( noted that it's been running rich)
3) timing on cranking checked =fine.
4) exhaust manifold temps checked ,=all 8 firing.
5) All idles and tickover screws all reset to base level
6) Started and will only run with almost all choke on
7) Fuel just drops in without choke pulled over suggesting not enough vacuum to atomise correctly rather than weak mixture.
Pulls cleanly with choke on but won't idle.
9) Removed all cables and pipework from carb to ensure no outside influences / leaking pipework.
When manifold removed ran wd40 through angled flange adapter no leaks.
Only leaves gasket between main body and spindle plate unchecked.
Valley gasket didn't look 'all that ' , certainly not the quality I'm used to not even the same as the pressed tin OEM with pressed out sealing edges.
