Just replace the carburettor diaphragm, Obtain part number 795083 for a couple of quid fom any sensible Lawnmower agent and away you go!
Go to you tube and find out how to change it- its not difficult and will save you a repair bill of anything up to £40-£50
pleasant
November 2011
Don't forget the air filter may be blocked.
davidj
November 2011
when was the last time you serviced this mower?if never then its time for a little TLC.drain engine oil ,replace the filters.take a trip to a mower, or garden center,most large garden centers sell ,stock mowers and someone there will be able to advise you on oil and service parts.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix lawn mowers.