Fixing the drive mechanism for a Yard man 4160?

Can anyone help me. My yard man wont drive forwards or backwards. I can see that the belt is still in place but there is a pulley/flywheel (?), just beneath the foot plate, that moves from side to side and has a spring hanging from it. If I knew where the spring was supposed to go I think that it would be cured.

Lesley
March 2009