Hi
Is this the newer briggs and stratton 11hp if so it as two elements to make it spark the flywheel with magnets on it and a coil. Make sure the flywheel especialy the magnets are clean and the pick ups on the coil are clean -if all ok and still no spark remove the wire in the middle of the coil this earths out the coil to make the mower stop and somtimes if you have a faulty ignition switch this can be permenaytly earthing out the coil causing no spark. If still no spark I cant see it being the flywheel so it must be a faulty coil.
Ps If its the older one with points its a bit more detailed let us know
Good luck
william
November 2007