Engine fails to start or is difficult to start

Possible cause may be :—

  • Throttle opened too far.
  • If cold, air lever in open position, or bad air leak at carburetter flange.
  • If cold, lack of fuel due to insufficient flooding of carburetter.
  • Lack of fuel due to stoppage in pipe, taps, or air lock in tank.
  • If engine hot, excessive flooding of carburetter.
  • Carburetter pilot system choked.
  • Sparking plug H.T. lead come adrift.
  • Sparking plug dirty or oiled up.
  • Sparking plug gap incorrectly set.
  • Sparking plug external insulator dirty or damp.
  • Sticking valves.
  • Broken valve spring.
  • Valves not seating properly.
  • Contact points dirty or incorrectly adjusted.
  • Dirty or wet high tension brush holder and lead.
  • Dirty slip ring or stuck pick-up brush.

Engine misfiring

Possible cause may be :—

  • Air valve not opened fully.
  • Defective or oiled up sparking plug.
  • Contact breaker incorrectly adjusted or points loose.
  • Tappet clearance incorrect.
  • Contact breaker points dirty or oily.
  • Valve springs weak.
  • Fuel supply restricted due to blockage.
  • High tension lead to plug faulty or insecurely fitted to magneto or suppressor.
  • Carburetter float punctured.

Loss of power

Possible cause may be :—

  • Sparking plug faulty or unsuitable type.
  • Insufficient oil in tank, or dirty or unsuitable oil.
  • Oil pump not primed.
  • Valve springs weak or broken.
  • Valves sticking or not seating properly.
  • Valve or ignition timing incorrect.
  • Piston rings worn or broken.
  • Engine excessively carboned.
  • Brakes sticking on or too closely adjusted.
  • Silencer tampered with.

Engine overheating

Possible cause may be :

  • Faulty lubrication. Insufficient, dirty, or unsuitable oil.
  • Oil pump not primed.
  • Sparking plug faulty or unsuitable type.
  • Air valve not opened fully.
  • Carburetter float punctured.
  • Engine excessively carboned.
  • Valve springs weak or broken.
  • Valves sticking, or not seating properly.
  • Piston rings worn or broken.
  • Valve or ignition timing incorrect.
  • Brakes sticking on or too closely adjusted.

Engine stops suddenly

Possible cause may be :—

  • Lack of fuel in tank or supply obstructed.
  • High tension lead come adrift.
  • Carburetter choked.
  • Carburetter float chamber air locked due to choked vent.
  • Fuel tank air locked due to choked vent in cap.
  • Sparking plug oiled up, or points bridged.
  • Water on high tension pick-up or sparking plug.
  • Water in float chamber.

Excessive oil consumption

Possible cause may be

  • Filter in crankcase restricted.
  • Fabric oil filter element requires replacing.
  • Air leak into crankcase at bottom.
  • Ball valve leaking.
  • Cylinder, piston, and rings worn.

Excessive fuel consumption

Possible cause may be :—

  • Fuel taps, pipe, or unions leaking.
  • Level too high in carburetter.
  • Punctured float.
  • Incorrect use of air lever.
  • Needle jet worn.
  • Needle incorrectly set.
  • Pilot air adjustment too rich.
  • Air filter choked.
  • Valve or ignition timing incorrect.
  • Brakes sticking on or too closely adjusted.