Today I tipped the mower on its side (oil fill down) and pulled off he blade and hub. Cleaned the grove of the hub so the belt would fit in the grove nicely and put it back together. Even without the new belt attached, the mower seems to turn over hard when I pull the pull start handle. I pulled the spark plug out and its easier, but does not feel right. Oil level if proper. Airens front self propelled with Kohler Courage engine.