Thanks to everyone for your replies.Sorry I haven't been on internet for a while but busy with work.
My YS 70DZ had the fuel line connected back to front straight from the factory and If you care to check the YS schematic diagram supplied it does show the fuel line in the wrong position as well hence it will not start.
Amazing that a manufacturer would miss this.
I have owned a feu YS engines now and personally the YS175CDI is the best so far but it is very disappointing when you don't get what you paid for

regards