My guess is that one or more of the pulleys on the mower deck is not moving. The smoke is from the belt rubbing on a pulley that is not moving or rubbing on some other object that is now in the belt's path. since the belt pops off, leave it off, turn off the engine to prevent accidents, then spin each of the pulleys on the mower deck by hand. They should all spin freely. Make sure that the deck is not clogged with grass or other debris. The springs that are hanging off are a problem as well. The belt must be routed properly and tensioned with the springs or it will fail quickly! Find a diagram or go see one at the store to see how the belt is routed and where those springs go.

I checked the pulleys, and it feels like the deck pulley may be stuck. I plan to take the deck off this weekend and take a look at it. Thanks for the tip!

I have a 10 year old MTD 17HP rider and when I disengage the deck, the deck belt starts to smoke and eventually comes off. All the pulleys turn and it cuts like a brand new one when I engage the deck. The belt actually looks loose when not engaged. Idea's???

The belt is suppost to be lose when the deck is off check to make sure the to rods are coming down from the frame and on the sides of the pully that hold the belt off of the pully when deck is off i replaced the screws on mine and mine no longer burns like it used to