Hi guys,sometimes you get so bogged down trying to rectify a fault,trying this and that with regular arobics pulling the cord when simple science comes involved.VACUUM caused by a non breathing fuel cap.loosend the cap,half a pull and wamo it kept running with a big smile on my face,adjusted mixture screw half a turn.I stopped and started the mower 10 times just to make sure,so thanks everyone for your thoughts and i owe you a beer BRUCE. ps-took my size 10 boot off and gave my-self a kick in the "but"...ken