Larger riding mowers, such as the Wright Sentar, Wright Stander, the Exmark Zero Turn and many others, use an electric clutch to engage the blades. While generally reliable, this type of clutch can occasionally fail and need to be changed. This is a job that, while not really simple, is still well within the capabilities of the average home mechanic. All lawn mowers using an electric clutch may not be engineered exactly the same, but there are enough similarities that you should be able to accomplish this repair easily.
Lift the mower high enough to work under it. Support it in this elevated position securely. If available, a lift table or chain hoist can work well for this.
Remove the safety covers to allow access to the blade drive belt tensioner. Release the tension and remove the belt from the pulley on the electric clutch. On the Wright machine, tension is removed from the belt by inserting a 1/2-inch square drive breaker bar into the square hole on the tensioner arm and turning the arm away from the belt. Other lawn mowers may use a spring loader tensioner or a mechanically adjustable one. Adjustable tensioners will have a threaded bolt that must be loosened to relax the belt tension.
Locate the plug to the electric clutch and disconnect it from the wiring harness. Push the clutch wire through the hole that it runs through on the mower deck.
Remove the bolt holding the clutch to the engine crankshaft. It may be necessary to loosen the 4 bolts which hold the engine to the mower deck and pry the engine up about 1/4 inch to have clearance enough to remove the bolt.
Slide the clutch off the engine crankshaft, noting the relationship of the slot and the means of preventing the clutch from turning. On the Wright machines, this is a piece of angle iron welded to the underside of the mower deck which is engaged by a slot in the clutch body. Other brands use a pin or bolt that fits into a hole in the flange of the clutch cover.
Slide the new clutch on to the engine crankshaft, making that the drive key is still in the slot in the crankshaft. Also make certain the proper slot or hole engages the device to keep the clutch from turning when engaged.
Place a small drop of Loctite medium-strength threadlocker on the clutch center bolt and thread the bolt into the crankshaft end. Tighten securely with a socket and the breaker bar.
Tighten the engine mounting bolts, if it was necessary to loosen them for clearance. Then connect the harness plug for the electric clutch.
Replace the blade drive belt and then start the engine. Test the operation of the electric clutch by turning it on. Replace the blade belt covers.