OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines 4hp Briggs and Stratton Quattro

Have you checked that you are getting a strong, consistent spark?

The symptoms are now a pretty good fit for a sheared flywheel key, resulting in grossly incorrect ignition timing, as rusty ute suggested earlier. Are you sure the key is OK? You need to remove the flywheel nut to be able to see it properly. You may even need to pull the flywheel off to check it definitively.