briggs and stratton classic 35 chugging?

hi my briggs and stratton classic 35 worked wonderful until i turned a corner whilst mowing then it just lost power and sat chugging, changed spark plug, added oil, added petrol, cleaned coil and disk but still problem persists, it still starts and runs but chugging very bad..i have been told to try a new coil but is there a cheaper idea out there before resulting to £50.00 lol
please help

mark
April 2009