Bike repairs continue

MY GN125 still seems to be having problems. It doesnt idle evenly, will rev up on its own and cut out too. It stinks of fuel, the plug is sooty black and yet we have turned the mixture screw right down. So far we have replaced the plug, had a new  diaphragm fitted in the carb (£35), had a new carb (£56) and a new inlet rubber (£16). It is gradually improving but still not perfect. It needs a new fuel tap now too – must go and order one – done! As with gardening, I am feeling way too cold to go outside and mess with it though!