1976 Cub cadet 1000 K241 10hp 44" deck. Seems to lose power while in the cut while mowing. I have noticed that while mowing it will pull down and sometimes puff a smoke ring out when losing power, like losing power and almost stall out. Have had this mower since 93 and motor was rebuilt in 90. It does not smoke and uses only 4oz-6oz of oil after mowing 2-3 acres. Spindles turn fine, belts seem fine, mule drive seems fine. Plug looked like it was burning way lean. Had white bubbles inside spark areas. Tried adjusting carb. But no clue what i was doing. Looking at carb the right screw I turned out from seat 2 turns, the top screw I turned 2 1/2 turns out from seat. Didnt seem to help and gas would spit out of carb on shut down. I messed with the govenor screw and picked up the rpm that way. Seemed to help some. Any ideas because I'm lost here.