Hi Guys,
Just to let you know. Popped in to Emile and Henrie in George. Poor okes were swamped with broken bikes and could unfortunately not fit me in - they obviously know it's pretty time consuming getting to that carb!
After having a long chat to them, got another new spark plug, cleaned air filter and air filter housing properly again and started a ride from Great Brak to George on all the dirt roads. Bike was running bloody well and stopped again in George for a heads up to Emile before tackling seven passes to Knysna and then on to Prince Alfred pass to Avontuur.
As I left Yamaha George - spluttering like hell again!!

Turned around, removed the plug - over fuelling again like crazy. Emile set the air on the carb to get it as lean as possible and off we go again. Better, but not close to what it should be.
We made it to Knysna, on flippen wet roads (great fun that was) and then turned around to avoid possible break down any further.
Will take it to KTM Centurion next week for proper diagnosis and repair. Definitely an over fuelling problem and I'll let you guys know what the final verdict was.
Thanks to Emile and Henrie, as well as you Dogs for the advice.