The game uses an electromagnet and a metal plate to bring the two wheels together to spin the inner wheel. To separate the plate and the magnet we use thin shims between them. Overtime the shims will wear down allowing the magnet to effect the wheel plate. Each game is unique and the spacing between the plate and the clutch can vary one games may only require 1 shim while another might require 3, see the shim replacement guide to determine how many your game will require. The part number for the replacement shim is VW1153