Service and Repairs

Troubleshooting
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Engine Cranks But Will Not Start
● Battery connected backwards.
● Blown fuse.
● Carburetor solenoid malfunction.
● Choke not closing.
● Clogged fuel line or fuel fi lter.
● Diode in wiring harness failed in open circuit mode.
● Empty fuel tank.
● Faulty spark plug.
● Fuel pump malfunction-vacuum hose clogged or
leaking.
● Fuel shut-off valve closed.
● Ignition module faulty or improperly gapped.
● Interlock switch is engaged or faulty.
● Key switch or kill switch in OFF position.
● Low oil level.
● Quality of fuel (dirt, water, stale, mixture).
● Spark plug lead disconnected.
Engine Starts But Does Not Keep Running
● Faulty carburetor.
● Faulty cylinder head gasket.
● Faulty or misadjusted choke or throttle controls.
● Fuel pump malfunction-vacuum hose clogged or
leaking.
● Intake system leak.
● Loose wires or connections that intermittently ground
ignition kill circuit.
● Quality of fuel (dirt, water, stale, mixture).
● Restricted fuel tank cap vent.
Engine Starts Hard
● Clogged fuel line or fuel fi lter.
● Engine overheated.
● Faulty ACR mechanism.
● Faulty or misadjusted choke or throttle controls.
● Faulty spark plug.
● Flywheel key sheared.
● Fuel pump malfunction-vacuum hose clogged or
leaking.
● Interlock switch is engaged or faulty.
● Loose wires or connections that intermittently ground
ignition kill circuit.
● Low compression.
● Quality of fuel (dirt, water, stale, mixture).
● Weak spark.
TROUBLESHOOTING GUIDE
When troubles occur, be sure to check simple causes which, at fi rst, may seem too obvious to be considered. For
example, a starting problem could be caused by an empty fuel tank.
Some general common causes of engine troubles are listed below and vary by engine specifi cation. Use these to
locate causing factors.
Engine Will Not Crank
● Battery is discharged.
● Faulty electric starter or solenoid.
● Faulty key switch or ignition switch.
● Interlock switch is engaged or faulty.
● Loose wires or connections that intermittently ground
ignition kill circuit.
● Pawls not engaging in drive cup.
● Seized internal engine components.
Engine Runs But Misses
● Carburetor malfunction.
● Engine overheated.
● Faulty spark plug.
● Ignition module faulty or improperly gapped.
● Interlock switch is engaged or faulty.
● Loose wires or connections that intermittently ground
ignition kill circuit.
● Quality of fuel (dirt, water, stale, mixture).
● Spark plug lead boot loose on plug.
● Spark plug lead loose.
Engine Will Not Idle
● Engine overheated.
● Faulty spark plug.
● Idle fuel circuit in carburetor plugged/restricted.
● Idle speed adjusting screw improperly set.
● Inadequate fuel supply.
● Low compression.
● Quality of fuel (dirt, water, stale, mixture).
● Restricted fuel tank cap vent.
Engine Overheats
● Cooling fan broken.
● Excessive engine load.
● High crankcase oil level.
● Lean fuel mixture.
● Low crankcase oil level.
● Cooling system components clogged or restricted.
Engine Knocks
● Excessive engine load.
● Incorrect oil viscosity/type.
● Internal wear or damage.
● Low crankcase oil level.
● Quality of fuel (dirt, water, stale, mixture).