How to Repair Yamaha Generators

by Brianna Collins

Yamaha Motor Corporation manufactures, in addition to its recreational vehicles and outboard motors, a line of industrial and commercial generators. In fact, in 2011 alone, Yamaha offered almost 20 different generator models on its website. Ranging from 1,000 to 12,000 watts, engineering differences exist between different models and years. Despite this, minor repair tips remain consistent across all models, and Yamaha offers similar troubleshooting advice in all generator owner's manuals to help owners handle minor repairs outside of the shop.

Quick Fixes

Check the engine stop switch, located on the far left side of the generator's front control box, if the engine stalls, misfires, or won't start. If it is set to off, turn it on. Otherwise, the engine cannot start.

Read the fuel gauge located on the top of the generator. If the fuel tank is empty, refill with unleaded gasoline and restart the motor.

Check the engine oil levels in the oil tank, located on the front of the generator underneath the control box. Unscrew the filler cap and peer inside. Engine oil levels should reach the upper level of the oil filler hole. If not, refill with oil until this level. The recommended oil for a specific generator is listed in the "Engine Oil" section of the owner's manual.

Tighten the cylinder head nuts, located on the front of the generator's engine, using a standard wrench.

Operate the recoil starter. If the engine still stalls or won't start, move on to the next section.

Spark Plugs

Use the recoil starter. If the engine does not even turn over, there may be something wrong with the spark plugs.

Remove the spark plug or plugs, located in each of the generator's cylinders on the front of its engine. Do this by removing the spark plug cap and rotating each spark plug counterclockwise with a spark plug wrench until it can be lifted from the cylinder.

Inspect the condition of the electrode end of the plug. If it appears brittle, cracked or burnt, the spark plug should be replaced with the kind of spark plug recommended in the owner's manual. The type and number of plugs varies according to model and year.

Measure the spark plug gap for each plug, which is the measurement of the gap between the hook at the end of the spark plug. Spark plug gap should measure the amount recommended in the "Spark Plug" section of the owner's manual, which also varies according to generator model. If the gap is too wide, shorten it by pressing this hook end against a hard surface. If it is too thin, widen it using a plug gap tool to gently pull the hook end wider.

Reinstall the spark plug or plugs by turning them clockwise into their respective cylinder holes with a spark plug wrench and returning the plug caps.

Try the recoil starter once more. If the engine still won't turn over, take the generator to a Yamaha dealer for inspection.

Fuel and Fuel Cock

Open the fuel tank and inspect the condition of the fuel in the tank if the engine turns over but won't start or if it stalls. If the gasoline is watery or gummy, it may be contaminated. Have a Yamaha dealer or mechanic drain the gas tank and refill it with fresh unleaded gasoline.

Turn off both the engine and the fuel cock lever to check the fuel cock. This lever is located on the right side of the generator.

Unscrew and remove the fuel cock cup and gasket, also located on the right side of the generator, using a standard wrench.

Inspect the inside of the fuel cock cup. If it contains build-up or debris, clean it out with solvent and wipe clean with a rag.

Replace the gasket if it is damaged.

Reinstall the fuel cock cap and gasket with a wrench.

Use the recoil starter. If the engine continues to run improperly, take the generator to a dealer for inspection.


  • check Yamaha recommends that owners consult a certified dealer for major repairs.


  • close Gasoline produces explosive fumes, so exercise caution while handling fuel and do not smoke while troubleshooting the fuel system.
  • close Using a spark plug other than the type recommended in the owner's manual for a specific model can cause irreparable damage to the engine.

Items you will need

About the Author

Brianna has been writing professionally since 2009. She has a Bachelor of Fine Arts degree and is excited to be part of a community that contributes to the free sharing of information and ideas.

Photo Credits

  • photo_camera rv,camp,caravan 3 image by mdb from