I've got the same issue with the Kawasaki FJ180V engine on mine. It surges at the strangest moments. The surging seems more prevalent when the weather is hot and humid outside. I don't know what's causing that. I contacted Exmark about the cutting issue. They responded by suggesting that I change blades to either their bagging blade or something called the extreme2 blade. Part numbers are: 108-3759 for the bagging blade and 108-0954 for the extreme 2 blade. I have no idea if either one would work.