ENGINE CRANKS BUT WILL NOT START

• Empty fuel tank.
• Fuel shut off valve closed.
• Fuel line clogged.
• Dirt or water in fuel system.
• Spark plug lead loss or disconnected.
• Ignition switch or kill with in OFF position.
• Transmission not in neutral.
• Spark plug failed.
• Spark plug improperly gapped.
• Ignition module malfunctioning.
• No or low compression.

ENGINE STARTS BUT WILL NOT KEEP RUNNING

• Fuel tank vent plugged.
• Dirt or water in fuel system.
• Choke cable malfunctioning.
• Throttle cable malfunctioning.
• Loose wires or connections that short kill terminal of ignition.
• Carburetor not adjusted properly.
• Cylinder head gaskets malfunctioning.
• Fuel pump malfunctioning.

ENGINE HARD TO STARTS

• Transmission not in neutral.
• Drive engaged.
• Loose wires or connectors.
• Dirt or water in fuel system.
• Clogged fuel lines.
• Choke cable malfunctioning.
• Throttle cable malfunctioning.
• Spark plug(s) malfunctioning.
• Carburetor not adjusted properly.
• Valve to tappet clearance set incorrectly.
• Low engine compression.

ENGINE WILL NOT CRANK

• Transmission not in neutral/drive engaged.
• Battery low or discharged, or not properly connected.
• Safety interlock switch engaged, not connected properly or malfunctioning.
• Loose or faulty wires or connectors.
• Ignition switch not connected properly or malfunctioning.
• Starter not connected properly or malfunctioning.
• Starter solenoid not connected properly or malfunctioning.
• Seized internal engine components.

ENGINE RUNS BUT MISSES

• Dirt or water in fuel system.
• Spark plug(s) leads loose.
• Spark plug(s) not properly gapped.
• Loose wires or connections that intermittently short kill terminal of ignition module to ground.
• Carburetor improperly adjusted.
• Engine overheating.
• Valve to tappet clearance set incorrectly.
• Ignition module malfunctioning.

ENGINE WON’T IDLE

• Stale fuel.
• Carburetor gummed up.
• Carburetor idle speed adjusting screw not set properly.
• Dirt or water in fuel system.
• Carburetor fuel idle adjusting screw not set properly.
• Fuel tank vent plugged.
• Spark plug(s) malfunctioning.
• Valve to tappet clearance set incorrectly.
• Low engine compression.

ENGINE OVERHEATS

• Grass screen clogged.
• Cooling fins clogged.
• Shrouding clogged.
• Excessive engine load.
• Oil level too low.
• Oil level too high.
• Carburetor improperly adjusted.

ENGINE LOSES POWER

• Oil level too low.
• Oil level too high.
• Air Filter clogged or plugged.
• Dirt or water in the fuel system.
• Excessive engine load.
• Engine overheating.
• Spark plug(s) malfunctioning.
• Carburetor improperly adjusted.
• Low engine compression.

ENGINE KNOCKS

• Oil level is too low.
• Oil level is too high.
• Wrong type of oil.
• Wrong type of fuel.
• Internal engine components worn or damaged.

ENGINE USES EXCESSIVE AMOUNTS OF OIL

• Wrong type of oil.
• Wrong oil viscosity.
• Clogged air breather assembly.
• Air breather assembly not assembled correctly.
• Worn or broken piston rings.
• Worn cylinder bore.
• Worn valve stems.
• Worn valve guides.
• Engine crankcase overfilled with oil.

ENGINE BACKFIRES

• Water in the fuel.
• Fuel level low.
• Bad fuse.
• Kill switch malfunctioning.
• Safety switch malfunctioning.
• Wrong fuel mixture.
• Worn valves.
• Choke or throttle not set correctly.
• Carburetor dirty.