I have admitted defeat and ordered a replacement carby. I think it's the air bleed that feeds around the emulsion tube in the middle of the carby, but I can't get to it without pulling the elbow welch plug and it will cost me almost as much as the new carby to replace it.
I started it up today to have another go at the idle mix, and unknown to me it was almost out of fuel, and as it leaned out it ran like a new engine, no black smoke, no vibration, so pretty sure the issue is carb related and not timing or a valve. We'll see I guess.
Last edited by Andy E; 09/03/21 05:36 PM.
