Bolen lawnmower, briggs stratton engine. The lawnmower will start on first pull, but only runs a minute or less, then stops. It will not restart for about 30 minutes, and yes the air filter is clean. Any suggestions?

Sounds like a fuel restriction. Did you check for a fuel filter? Also check fuel flow from fuel tank and then there is the possibility of fuel blockage in the carb. You could verify this by carefully spraying a LITTLE starting fluid into air intake as it starts to stall out. If it picks back up for a second or two then you know you definitely have a fuel restriction.

Good luck,
Morrowrj