I have an early 90's model Briggs 16 HP Vanguard that started surging over the weekend. It was running fine all afternoon, but when I dropped it down to idle before putting it away I noticed that it was surging badly. It surges at idle or part throttle, but smooths out at higher RPM's. Applying patial choke seems to smooth it out. My first thought is that I picked up some crud in the fuel. Does anyone have some ideas to try out before I look into removing the carb and going through it? Air filter is clean, fuel filter (clear) does not appear to have anything blocking it. Thanls for any suggestions!