What exactly is "irregular"?
Generally speaking, from my experience, 95% of small engine problems are carb related. You may think the carb is clean but, chances are, it isn't. However, prior to pulling it apart and cleaning it, ensure that your fuel is fresh and free of water and dirt. Make sure the carb is getting unimpeded fuel flow all the way from the tank to the float bowl. If it is, and the fuel is clean, take another look at the carb.
I'm surprised that fit!