Ok guys,
I have been tinkering - for want of anything else to do!!
Checked everything ...again...and all good.
Got new fuel and filtered it twice and put in clean glass container so cannot have contamination there.
All timing marks checked and all in 'correct' positions.
Will start after a few cranks on full throttle but still having trouble keeping it running. It starts, revs up then seems to run out of fuel and dies (regardless of revving etc.) It will restart again but does exactly the same.
So,
Tinkering commenced....
I adjusted the timing on pump one cog clockwise and tried that.....it didn't make much difference except took longer to start and the smoke got a little bluer....
So, moved another cog.....this time wouldn't start.
So, went back to the beginning and tested - started but stopped again. So, I went the other way but 2 cogs didn't make it run properly.
Once again I'm at the end of my tether with this piece of crap.
Any thoughts?