The machine is a Husqvarna R53W, two years old. I have never had problems starting it & last used it two months ago. Now when I try to start it, it only fires briefly perhaps one in ten pulls and often kicks back in mid pull, yanking the pull cord back to the engine. I have a reasonable working knowledge of engines, have checked the spark plug and it sparks OK and is clean, and changed the fuel to ensure no contamination. I have noticed that when the lever is put to the 'Start' position and then moved to the 'run' position that the carb butterfly does not move but perhaps airflow operates this as I see it has a balancing spring? Have you any ideas what may be the problem? Many thanks

Charles Brocket, August 2008

Thanks so much for your answer. Where exactly is the flywheel key?!

Charles Brocket, August 2008

Have you checked the Flywheel key. from what your saying that's what it sounds like. if the key is sheared that will throw the timining of and will cause it to backfire and also rip your hand off. check underneath the mower for any blade damage or other evidence of hitting something. Check your blade adapter for damage and missing pieces. Best of luck........

Don't forget to check the oil.

rexter1@excite.com, August 2008