hi
had the same trouble with mine
what you want to do is clean the air filter also
if you know where the engine tries to fire
(should have five orange leads coming out of it (small cylinder two size ten bolts) take this of and clean inside here) also make sure your water level isnt to high should be about half way filled and finally at back of engine near windscreen theres a compartment screwed in with two phillips screws (big ones) take the lid of and turn engine on if petrol is coming into section fine then theres no petrol block if not you have a petrol blockage and this can cause the engine to do what you are describing>> i did all the above and have yet to have a problem again (touch wood)
hope this helps sorry bout description im not sure of all the mechanical names
jay, October 2009