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

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 trys 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
I'm not real sure about a Bolen but my homelite had a similar problem and it was the fuel pump, a type of flexable rubber or fiber piece that flexes with the running of the engine and pumps the fuel. Sorry for explanation but it's the only way I can explain it.

Try And Get A Rebuild Kit For Your Carb. Some Carbs. Have To Be Replaced As They Have No Kit Available. Then After Rebuild, Screw In The Low And High Mixture Jet All The Way, Then Back The Low Jet Back Out One Full Turn, And The High Jet Two Full Turns, Go From There To Set The Carb.
Please Rate My Answer If This Helps.
Thanks, Mowerman2468