Cause 1

PTO Switch

The PTO switch provides power to the PTO clutch. If the switch is defective, it may not supply power to the PTO clutch. As a result, the clutch won’t engage, and the lawn mower blades won’t rotate. To determine if the switch is defective, use a multimeter to test it for continuity. If the PTO switch is defective, replace it.

Cause 2

PTO Clutch

The PTO (Power Take Off) clutch provides a means of manually disconnecting the engine from the blades. When the clutch solenoid is energized, the clutch engages the drive belt to drive the rotation of the lawn mower blades. If the PTO clutch is not getting power, if the clutch solenoid is defective, or if the clutch is worn out, the lawn mower blades will not engage. The PTO clutch is not repairable—if the clutch is defective, you must replace it.

Cause 1

Fuel Cap

As fuel is consumed by the engine, the level in the fuel tank lowers. To make up for this, the fuel cap uses a small vent to allow air to enter the tank. If the fuel cap vent is clogged, air won’t be able to enter the tank and a vacuum or “vapor lock” will occur. This stops the flow of fuel to the carburetor causing the engine to stall. To determine if the fuel cap vent is clogged, try slightly loosening the cap and then starting the engine. If loosening the fuel cap allows the engine to stay running it is likely clogged and will need to be replaced.

Cause 2

Carburetor Repair Kit

The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the lawn mower for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the carburetor and cause the engine to stall. If the carburetor is clogged, try cleaning it with carburetor cleaner. If cleaning the carburetor isn’t effective, rebuild or replace the entire carburetor.

Cause 3

Carburetor

The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the lawn mower for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the carburetor and cause the engine to stall. If the carburetor is clogged, try cleaning it with carburetor cleaner. If cleaning the carburetor isn’t effective, rebuild or replace the entire carburetor.

Cause 1

Spark Plug

Inspect the spark plug for signs of wear or damage. If the porcelain insulator is cracked, an electrode is burned away or damaged, or there is heavy carbon buildup at the electrode, replace the spark plug. To determine if the spark plug is defective, use a spark plug tester. You should see a strong spark between the tester’s terminals when the engine is cranking. If there is no spark, this indicates that the spark plug is defective and should be replaced.

Cause 2

Carburetor Repair Kit

The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the lawn mower for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the carburetor and cause the engine to run roughly. If the carburetor is clogged, try cleaning it with carburetor cleaner. If cleaning the carburetor isn’t effective, rebuild or replace the entire carburetor.

Cause 3

Carburetor

The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the lawn mower for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the carburetor and cause the engine to run roughly. If the carburetor is clogged, try cleaning it with carburetor cleaner. If cleaning the carburetor isn’t effective, rebuild or replace the entire carburetor.

Cause 1

Carburetor Repair Kit

The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the lawn mower for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the carburetor and prevent the engine from starting. If the carburetor is clogged, try cleaning it with carburetor cleaner. If cleaning the carburetor isn’t effective, rebuild or replace the entire carburetor.

Cause 2

Carburetor

The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the lawn mower for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the carburetor and prevent the engine from starting. If the carburetor is clogged, try cleaning it with carburetor cleaner. If cleaning the carburetor isn’t effective, rebuild or replace the entire carburetor.

Cause 3

Spark Plug

Inspect the spark plug for signs of wear or damage. If the porcelain insulator is cracked, an electrode is burned away or damaged, or there is heavy carbon buildup at the electrode, replace the spark plug. To determine if the spark plug is defective, use a spark plug tester. You should see a strong spark between the tester’s terminals when the engine is cranking. If there is no spark, this indicates that the spark plug is defective and should be replaced.

Cause 1

Clogged Cooling Fins

All air-cooled small engines have cooling fins manufactured right into the engine's cylinder head and short block. These fins help to dissipate the heat from the engine. If the fins get clogged with dead grass, leaves, or other debris, they won't allow the engine to cool properly, and the engine will overheat.

Cause 1

Alternator

The alternator provides power to the lawn mower while the engine is running and recharges the battery when the engine is not running. If the lawn mower has headlights, turn on the headlights and then turn off the engine while watching the headlights. If the lights dim when you turn off the engine, the alternator is working properly. If the lights do not dim, the alternator is likely defective. To determine if the alternator is defective, use a multimeter to test the alternator voltage output according to the wiring diagram.

Cause 2

Charger

To determine if the charger is defective, use a multimeter to test the charger for continuity. In addition, test the outlet used by the charger, and ensure that the outlet has not tripped a breaker.

Cause 3

Alternator

The alternator provides power to the lawn mower while the engine is running and recharges the battery when the engine is not running. If the lawn mower has headlights, turn on the headlights and then turn off the engine while watching the headlights. If the lights dim when you turn off the engine, the alternator is working properly. If the lights do not dim, the alternator is likely defective. To determine if the alternator is defective, use a multimeter to test the alternator voltage output according to the wiring diagram.

Cause 1

Carburetor Repair Kit

The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the hedge trimmer for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the carburetor and make the engine hard to start. If the carburetor is clogged, try cleaning it with carburetor cleaner. If cleaning the carburetor isn’t effective, rebuild or replace the entire carburetor.

Cause 2

Primer Bulb

Over time, the rubber of the primer bulb can become brittle and cracked. If the primer bulb is cracked, air will get into the fuel system and cause the engine not to run properly. If the primer bulb is cracked, replace it.

Cause 3

Carburetor

The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the hedge trimmer for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the carburetor and make the engine hard to start. If the carburetor is clogged, try cleaning it with carburetor cleaner. If cleaning the carburetor isn’t effective, rebuild or replace the entire carburetor.

Cause 1

Carburetor Gasket

If fuel is leaking from the bottom of the carburetor, the carburetor gasket might be dried out or missing.

Cause 2

Float Needle

The float needle might not be shutting off the fuel. The float needle opens and closes the float valve to allow fuel to enter the float bowl. If the float needle is damaged, the carburetor will continue to fill with fuel until it overflows. If the float needle is defective, replace it.

Cause 3

Carburetor Bowl Gaske

If the lawn mower leaks gas the carburetor bowl gasket on the bottom of the carburetor might be dried out or missing. If the leak is coming from the bottom of the carburetor, try replacing the carburetor bowl gasket.

Cause 1

Carburetor Repair Kit

If the lawn mower engine produces black smoke, this indicates that the carburetor is getting too much fuel (or "running rich"). If the carburetor float is stuck closed, the engine will get too much fuel. Similarly, if the carburetor choke is stuck closed, the lawn mower engine will not be able to draw in enough air to create the proper air-fuel mixture.

Cause 2

Carburetor

If the lawn mower engine produces black smoke, this indicates that the carburetor is getting too much fuel (or "running rich"). If the carburetor float is stuck closed, the engine will get too much fuel. Similarly, if the carburetor choke is stuck closed, the lawn mower engine will not be able to draw in enough air to create the proper air-fuel mixture.

Cause 3

Carburetor is Letting Too Much Fuel In

If the lawn mower engine produces black smoke, this indicates that the carburetor is getting too much fuel (or "running rich"). If the carburetor float is stuck closed, the engine will get too much fuel. Similarly, if the carburetor choke is stuck closed, the lawn mower engine will not be able to draw in enough air to create the proper air-fuel mixture.

Cause 1

Wheel Assembly

The wheel assembly has a set of gears which engage with the transmission drive gear. If the gears are worn out, the transmission won’t be able to engage the wheel assembly. If the gears are worn out, replace the wheel assembly.

Cause 2

Drive Pulley

The drive pulley connects to the engine crankshaft. If the drive pulley is worn out or broken, the transmission won’t be able to engage the wheel assembly. Inspect the drive pulley for damage. If the drive pulley is defective, replace it.

Cause 3

V-Belt

The V-belt rotates the drive pulleys to drive the lawn mower wheels. If the V-belt is worn out or broken, the lawn mower wheels won’t turn. Inspect the V-belt for damage. If the V-belt is defective, replace it.