lawmower

I have a Hyundai 510sp lawnmower that is surging and I can't figure out what's wrong. I've cleaned the carburettor about 5 times with carburettor spray and enlarged the 2 valves slightly with a micro drill bit. All the little holes are clear. It was fine last year but I did leave fuel in it over...

All, Apart my CRV headache with vibrations got friend coming on Friday evening for a beer and he took with him a non runner Partner 471 lawnmower. I cleaned up carburettor and bum started at first shot. Got him to cut my grass :) and engine worked very well. he then stopped to removed grass box...