Check the plug wire. A lot of them are carbon track core meaning there is a carbon coated string in the center. If the cap is mis-crimped on the string over time it becomes unreliable and just stops conducting. Had this issue with a Kawasaki vertical twin. One side was intermittent then just quit. Replaced the cap with a screw on NGK replacement. LB01EPJohn Deere LA 115 19.5 briggs and stratton starts cold runs 5 minutes and cuts off. loses spark. Has a new spark plug new gas filter, new air filter. Anyone else have this problem?