I have a 16 HP B&S engine on a snapper mower. It was built in the mid to late 80's and will not operate unless I leave the choke about a 1/4 of the way out. As a result the plugs quickly foul-up and the engine lacks some of its old power. I have changed the plugs and the fuel filter.
Does anyone have an answer/fix for the problem?

the low sde of the carburator is plugged up you are going to have to clean it good
you can clean it without taking it off the intake get you some carb spray and clean with spray and air take out the air fuel mixture screw out and blow it out good ,