1. Take out the Seat.
2. Weld together any broken springs.
3. Use a "Pool Noodle" ($1 at any dollar store or grocery store) and cut it up and stuff your seat with it.
4. TIE the pool noodle chunks to the springs with zip ties or wire.
With my broken spring, I just folded up some foam and put it up there.
http://www.dieselgiant.com/repairseatspring.htm Great Guide