Briggs and stratton won't stay running until hot
I have a 5HP B & S engine on a log splitter. Until this year it has run perfectly for 15 years. This year it won't stay running until it gets hot. It starts very easily but runs less than a minute (maybe as much as fuel in the carb from the pull start ?) I restart it 2-3 times before it will continue running on it's own. I've changed the spark plug & oil, checked the exhaust for blockage and run 3 tanks of fuel through the system since this started. There is no in-line fuel filter, just an in-tank material that looks like a full sponge. It doesn't look like the fuel tank can be easily removed and that filter replaced. Any suggestions? I can keep running it the way it is since eventually it does work but I also don't want to damage it. I'd just as soon determine what has changed and correct it. THANKS !
Jch