thanks again Grumpy. I fitted a new spark plug and same thing..
I then removed the carb, cleaned all the nozzles, diagphragm etc then refitted and still no good.. it just does not want to run without throttle applied

as soon as i lift the hand off the throttle it dies instantly.
what i know is that it is ryobi rbcgm25ss machine 25.4 cc with Ruixing carb and it is the latest model.
I am really puzzled to what it can be ..