Briggs and Stratton 550 self propelled/Poulon Pro.
Have replaced the spark, cleaned the carb(with carb spray), replaced the oil/checked the oil level and installed a new breather. When I start the engine the engine runs strong at first, then slowly the RPMs get erratic and eventually(maybe after15-20 minutes) stalls out. During the time it's running, sometimes the white smoke starts to diminish, but then will start up again.
As the engine is sputtering, could this be a bad carb? I may have accidentally tipped the mower the wrong way.
Tipping the wrong way will allow oil to run into the breather and get transferred over into the carb. I have seen the carb bowls get totally full of oil from this.
As it starts ok me thinks your problem is still in the carb.
Firstly check he oil level very carefully you will most likely find it high.
Check the float bowl chances you will fins oil in there.
remove the breather from the carb & put some sort of catch bowl under it
Try again and see what happens.
