Not my machine, friends, but here goes. About a 5-6 year old 52" Exmark Z with either a Kohler or Briggs engine, I think it is a Briggs. Can mow for a while then it will shut off. Starts right back up and will run for a while then does the same thing again. Replaced the fuel filter but still does the same thing. Electrical? Fuel Pump? Any ideas/experiences? Thanks.