Had issues with the B&S Vanguard on the Pro-16 running rough, surging, etc. When it does this when the PTO is engaged, the 50" deck mounted to the A-frame goes into a weird oscillation until I take it out of Hi or Low, at which point you can hear the engine surging to a cadence. I replaced the fuel filter after cutting about half the back yard when it started to act up. Wanted to get into the carb. but wasn't sure if these are intended to be adjusted. Anyone have experience with these that can offer a remedy?