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Opal fuel - trouble shooting

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.


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

Problems

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.