Hoping to find a solution here. I'm working on a 2011 Troy Bilt Pony model 13WN77KS011. The issue I just can't figure out is a bad vibration when the blades are engaged. The engine runs good and very smooth when not spinning the blades. This is a mower I bought not running for a flip. I have completely rebuilt the deck with all new components (some I replaced while chasing this issue), as well as a new belt and blades. As soon as you engage the blades, the entire mower shakes. I first assumed an imbalance in the blades, so I took them off and it didn't change. While it's not as bad, it's still there. I have gotten down low to observe the deck drive assembly while running and can see the shaking in several areas. Thinking it was the idler arm, I took it off and recentered the worn, ovaled pivot hole by welding it back in and redrilling it, with the same results. Someone suggested a bent crankshaft, but I think I would see visual signs of it in the crankshaft pulley while spinning, and I don't. My next step was going to be swap belts, but I've got my doubts. Anyone run into this on a rider of any breed? I have attached a link to a video of the deck components running at a low rpm. It gets worse as the rpms increase.