I have a craftsman riding mower 917.270641. It's old but runs good. What's started to happen is when I push up on the blade engage lever, It feels very stiff, like it's restricted or somethings binding it. I've tried it with the deck all they way down and all the way up. Sometimes it won't engage the blades at all, I can push the lever all the way and hook it and it wont engage. It acts worse when the deck is all the way down. When I attempt to engage the blades the lever feels free, then starts to grab on something and gets real hard to push, then with a snap it engages the blades. It's not smooth at all. But when I disengage it is smooth release and does not feel like its binding up on something. I have to push on the lever hard, real hard, it seems too hard and even sometimes it goes all the up and does not engage if the deck is all the way down, it seems to do better when it deck is about halfway or all the way up. I've looked and looked and I can't see the pullys catching or binding on anything that I can see. I know it's something going on with the idler pully on the deck but what? Does anybody have any ideas about how to fix this? Thanks!