My wife had a similar episode to the one posted where she filled our lawnmower way above the fill line. She ran the lawnmower briefly. I dumped the extra oil out and the mower has sat for the winter. I've replaced the plug three times. The mower will run good for a few minutes and then start to surge. When I pull the plug it is black. The air filter is clean. The gas is new. I've ran it surging through a whole tank of gas. I'm concerned the problem may be rings. Does anyone have any thoughts? It's approx. two years old and a small B&S. If it needs rings, is it worth it? The mower was $189 new. Any input would be appreciated.

did you happen to use any fuel stabilizer in the previous gas, because if you never ran it out, it probablly got gummed. but you never gave hp, so it could be a float carb, or a diapragm

No, I didn't use stabilizer. 4.75 hp. You think I should take a look at the carb? I really appreciate you taking the time to give your input. It would make my wife happy as well if the problem is that simple. Probably wouldn't hurt either if it was my fault for not using stabilizer instead of hers.

well. the overfilling of the oil, can cause rings to break, but if caught in time, i wouldn't worry right now, after you take a look at the carb, then check the bore if not the carbs fault

I took the carb apart and cleaned it up this A.M. before church. I put it back together and it runs fine. I feel a little sheepish for not picking that one up on my own. Many, many thanks.-KN

great! now do use some stabilizer if the fuel you are going to use is going to set a while, i wouldn't go over 3 weeks with untreated gas. and when you put the mower up, run some stabilized gas in it to prevent it from happening again. oh and the oil, fill in increments till just slightly above the full line. some will think to add a whole quart, but they can't hold that.

Just as a starting point...

Most push mower engines hold about 2/3 of a quart.

Most riding mower engines hold about 1 and 1/3 quarts.

Use these starting points then add oil as necessary.