Over easter; I pull the tank off, disconnected the air box and pulled it back, unscreewed the inlet boots readly to pull the carbies.
Also pulled the carbs tops off and clean the sliders (some dust on each one).
It was getting late, so I put every thing back.

Bike runs sooo much nicer, problem is still there but barely.
I also notice that the vacuum hose was a bit tight; maybe the previous owner had cut the ends off to fix it.
Have now replace the hose, but not ridden it since.

I'm pretty sure I read the numbers on the cabbie diaphragm rubbers numbered 4 on cylinder-4 and 3 on the others, ???