Funny. My almost new red Toro mower (22" or so) finds it very hard now to propell itself. makes it soooo hard to push a "self propelled" mower, fighting with stuck gears and all, I figure. Any idea where I should start to look for work/out of adjustment parts?
If it is less than two years old, back to the dealer, under warranty. Over two years old I would suspect that you have something wedged between the belt and the pulley.