Report part 2:
I got a new plug (ngk is my preferred), and a tin of carby cleaner, did the pull-apart of carby, checked and cleared jet holes, flushed passages with the cleaner. Didn't notice any issues to speak of, I'll post some pics later. The 'rubber' gasket between carb and air cleaner bracket has gone 'gooey', wonder if this is common or has somebody dissolved it with a harsh chemical? In any case, I don't think that is part of the problem.
Checked the cold valve clearances and found them to be perfect.
I reassembled, test ran, maybe slightly improved, I got the compactor to run one time nearly right, but next try was back to previous behaviour and motor stalled when asked to load up.
Given that I was now confident the motor should be in good order I turned my attention to the vibrator unit (also called an exciter). Bingo...problem located, bearings damaged and dragging. I didn't know what to expect in there, but it's a simple 'out of balance' shaft with open roller bearings at each end. Problem is that being open rollers they need oil, and there was zero oil in the housing...
I studied the sales brochure for the current model of this unit (Easymix 550H) which says 'sealed bearings, no oil required' so I will replace the open rollers with sealed bearings ASAP and will expect it to run up nicely after that.
Will post pics soon to enhance the thread for future lookers
