Signs & Symptoms of a Faulty Starter Clutch on Lawn Mower Engines

Starter Clutch Applications

• Starter clutches are not used on electric start engines, where a conventional starter motor with an extending-retracting drive pinion engages with a flywheel. They are therefore uncommon on ride-on lawn mowers and tractors, and more common on walk-behind units.

Signs and Symptoms

• Problems can include the sticking of the tiny ball bearings that allow the clutch to rotate, and the freezing up of the gear in the engaged position. These issues are more common in machines that are left outside than in ones stored in a shelter. The most common symptom of the first problem is a loud rattling noise from the area where the pull rope disappears into the pulley housing as soon as the engine starts. The latter problem causes the pull-rope to not be retracted after reach pull; it may retract partially, or the full length may simply hang in mid-air. Alternately, the pull-rope may initially retract into the rewind assembly, then feed out again as the engine runs.

  Ignoring the early symptoms of starter clutch failure is not recommended. The unit will eventually fail, perhaps at an inconvenient time, and collateral component damage could occur.

A Further Consideration

• There is a second clutch on some walk-behind lawn mowers: the blade brake clutch. Although not part of the starting mechanism, a fault in this assembly can prevent starting. The blade brake clutch is intended to allow the engine to run without turning the blades, but some units have sensors on them that cut out the engine if they sense a problem such as the blade encountering a very resistant object. If this sensor malfunctions, it can prevent the engine from starting.

Unrelated Problems

• Starter clutch problems should not be confused with other issues that can cause difficulty in starting, or prevent starting altogether. If the symptoms specific to the starter clutch are not presented, then check the spark plug and wire function, fuel level and quality -- gasoline goes “stale” if left over the winter without the addition of a stabilizer -- and the condition of the fuel and air filters.