Well I think things are sorted Engine is running so much nicer today. After a bit of messing around, much thinking, and a light bulb moment, i realised the governor was fully open at half throttle, this explains the flatness. There is no way on earth this engine ran nicely, if at all, before it was removed by the last owner. With this set right i could then tweak the fine tuning and all seems good. There was a slight odd misfire, one when increasing the revs from idle and then intermittent on full revs, but this seems to have cleared up with some driving round the garden. I will test again tomorrow from cold and make sure So then got on and put my cement mixer back together. The real test will be fitting the cutting deck or pulling a trailer load of mud around can't wait!
Thanks all