I have a Craftsman 917.375500 that is barely pulling itself and won't pull uphill. There's a plastic cover over the pulley and that area instantly fills up with grass (and blows some out of it since the cover doesn't fit tightly), so I'm wondering if that's aftecting it. I know I should try a new belt too. My dad gave me the mower and he mentioned that it used to have baffling underneath so I'm wondering if that hole under pulley used to be blocked to prevent the grass from getting in that upper area. I can't find any such part on the parts diagram though:
