Hello, I am having problems with my hustler 66 cut 27hp air cooled kohler. Just replace battery at the end of summer last year and this year it starts right up as usual but when I engage blades I get a large power loss. If I am moving and engae the machine lags enough to almost throw me off. Once the blades get to speed and I try to cut the mower immediately bogs down and stall. Whne I try and restart I have to open the choke slightly to get it restarted and it will do the same thing again. Plz advise as I need to get cutting.