Troubleshooting

The following list provides a variety of common problems and most probable causes. Whilst many problems are listed, not everything that can go wrong is covered. However, it can be a starting point for guiding you in the right direction.

Note: always seek advice from a qualified repairer.

Problems

Click on the relevant problem below to see a list of the possible causes

Engine will not start or is hard to start

Possible causes:
  • Fuel is stale and has carbonned the spark plug
  • Fuel tank is empty or shutoff valve is closed
  • Fuel line or fuel tank cap vent is clogged
  • There is water in the fuel
  • Carburetor is over choked
  • Carburetor is improperly adjusted or needs service
  • Ignition system or its wiring is defective or ignition switch is off
  • Dead man or other cutoff switch is open or defective
  • Spark plug is fouled, improperly gapped, or damaged

Engine starts easily but dies after a few seconds

Possible causes:
  • Fuel tank is empty or shutoff valve is closed
  • Fuel line or fuel tank cap vent is clogged
  • Carburetor is over choked
  • Carburetor is improperly adjusted or needs service

Engine idles roughly, unevenly, or surges

Possible causes:
  • Carburetor is dirty
  • Air leak in carburetor or intake manifold (e.g. bad O-ring, gasket or primer)
  • Carburetor is improperly adjusted or needs service

Engine misses under load

Possible causes:
  • Spark plug is fouled, improperly gapped, or damaged
  • Breaker points are pitted or improperly gapped, or condenser is bad
  • Carburetor needs adjustment or service
  • Fuel line, fuel filter, or fuel tank cap vent is clogged
  • Fuel shutoff valve partially closed

Engine knocks

Possible causes:
  • Carburetor is set too lean
  • Incorrect octane rating fuel used
  • Engine is overheating
  • Carbon buildup in combustion chamber

Engine lacks power, possibly after warm-up

Possible causes:
  • Old or stale Petrol
  • Spark plug is fouled, improperly gapped, or damaged
  • Very thick or dirty oil (4 Stroke)
  • Choke is partially closed
  • Carburetor needs adjustment or service
  • Air filter is clogged
  • Head gasket blown or damaged

Engine operates erratically, surges and runs unevenly

Possible causes:
  • Fuel line or fuel tank cap vent is clogged
  • There is water in the fuel
  • Carburetor needs adjustment or service
  • Loose carburetor or intake pipe resulting in vacuum leak

Engine overheats

Possible causes:
  • Carburetor set too lean
  • Air intake or cooling fins are clogged
  • Excessive load
  • Insufficient or excessive oil
  • Improper oil viscosity (4 stroke) or mixture (2 stroke)
  • Excessive carbon buildup in combustion chamber

Crankcase breather passing oil

Possible causes:
  • Too much oil in crankcase
  • Engine speed is excessive
  • Oil fill cap or gasket is damaged or missing
  • Breather mechanism is dirty or defective
  • Piston ring gaps are aligned
  • Piston rings are worn

Engine backfires

Possible causes:
  • Carburetor set too rich
  • Spark plug has fouled and is firing intermittently

Summary

Always ensure your equipment is up to date with maintenance, use fresh fuel or 2 stroke fuel mixes. If in doubt consult your equipment manufacturer.