Yamaha Coolant or Unburned Fuel in Exhaust

Generator emits white smoke or steam from the exhaust, especially on startup.

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Condensation in exhaust (normal short-term), Coolant leak into combustion chamber (head gasket), Injector dribbling fuel (diesel), Low combustion temperature

How to Fix / Troubleshooting

Safety first: Operate in a ventilated area. Avoid breathing exhaust fumes.

  • Observe duration: Light white vapor that disappears after warm-up may be normal condensation. Persistent thick white smoke indicates a problem.
  • Check coolant level: Monitor coolant level over several runs. A dropping level with white smoke suggests internal coolant leak; contact a Yamaha technician.
  • Inspect oil: Milky oil indicates coolant contamination. Do not run the engine; seek professional service.
  • Injector service: On diesel units, have injectors tested and serviced if unburned fuel is suspected.
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Repair Difficulty

Professional Required 5/5

Required Part

Cylinder Head Gasket
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