Briggs & Stratton 4HP engine runs rough
Engine starts and runs, but smokes and runs very rough. I believe the fuel mixture is too rich becasue it runs perfectly just before it runs out of gas in the tank. I have changed plug, the gas cap vent hole is clear and there is no difference when the air filter is removed.
Any suggestions on how to fix this? There don't seem to be any adjustments on the carb.
This is on a Murray mower and the engine numbers are:
Type: 2291 B1
Thanks for any advice anyone can offer.