I was wondering if there is something that would make the magnetos go bad on this engine. Was on here a couple months ago with problems on this engine and ended up replacing a magneto on one side and rebuilding the carb.

Today went to work, engine started and ran fine for about five minutes and stopped. Will not start again. Checked spark and have no spark on either side now. Plugs only two months old and look pretty bad so I am going to replace them and hope that it is just fowled plugs. If not, looks like magnetos again and one is new. 1. why would the plugs fowl so fast and 2. what would cause the magnetos to go bad like that?