Briggs & Stratton 3.5hp Model 98902
I have a Bolens Edger with a 3.5 Vertical Shaft Briggs which I purchased used with this problem: After priming the carb, the motor will start (it may take a couple of tries to keep it running) Once it keeps going, the engine seems to oscillate (revs up and dies down, revs up and dies down continually.) While it does that, it shoots black smoke (rich) from the exhaust.
It has fresh gas and a new spark plug.
Can you give me some ideas as to what may be wrong?
Thanks, Dan