I took the air filter pipe off the carb and was looking down at damper piston to see if the fluctuations had stopped. It's still fluttering and when I lift it with a screwdriver it feels like the first 4mm of so of travel is not damped and only after that does the damper add some resistance. Need to figure out if this is normal.
When looking at the piston, I noticed that the sides of the carb between the piston and butterfly was visibly wet with fuel. I shut off the engine but left the ignition on so that the fuel pump was still running. I undid the 3 screws of the dashpot assy, lifted it off and found there was a puddle of fuel at the bottom of the butterfly.
It looks as though fuel is seeping up the jet. So either the float level is wrong or something isn't right on the bottom of the carb.
Will strip it down and double check float.
I'll add a video later to show what I mean.
Oh and I try to keep the birds nest of relays and wires out of shot in the engine bay. Too embarrassing, needs to be tidied up!
Drove fine for a few days and then started acting up big time the other evening. Whipped the dash pot off and puddle of fuel behind the butterfly again.