Visible oil leak under the generator set or oil pooling in the base pan.

Safety first: Turn OFF the generator, disconnect battery negative, and allow the engine to cool. Clean up spilled oil promptly to avoid fire hazards.

• Locate leak source: Wipe down the engine and then observe where fresh oil appears during a short run.
• Check drain plug: Tighten the oil drain plug to Yamaha torque spec and replace its washer if damaged.
• Inspect oil filter: Ensure the oil filter is hand-tight plus the recommended additional turn. Replace the filter and its gasket if leaking.
• Gasket inspection: Look for seepage at the valve cover and crankcase gaskets. Replace gaskets if necessary.
• Refill and test: Top up engine oil to the correct level and run the generator while monitoring for further leaks.