Home & Garden Maintenance & Repairs

Stihl 660 Chainsaw Troubleshooting


    • 1). Check the chain tension. If yours is properly adjusted, you should be able to pull the chain away from the bar about 1/4 inch. If it is loose, remove the sprocket cover and use the screwdriver or adjustment tool to tighten it down to the proper tolerance.

    • 2). Observe how your chain behaves when the saw is running. A sharp chain will chip out wood into bits resembling the pages of a book. If your chain is producing only sawdust or seems to be cutting slowly, it has become dulled. Remove it from the chain bar and sharpen it with your chain file or bench mounted chain sharpener before reinstalling it.

    • 3). Check the condition of the cutter and raker links on the chain. If they have been ground down from repeated sharpenings, the links can no longer cut efficiently because so much of the metal has been removed previously. Discard the old chain and purchase a new one of the appropriate length.

    Spark Plug

    • 1). Note how much power your saw develops when it is running. If the engine stalls once it is hot, it is a sign that your spark plug may be worn or fouled with carbon buildup.

    • 2). Remove the top cowling unit using your Stihl-supplied adjustment tool or slotted screwdriver. This action will expose the spark plug.

    • 3). Slide the spark plug wrench end of your adjustment tool onto the plug and use a counter-clockwise turning motion to remove it.

    • 4). Check the sparking electrode at the base of the plug. If it is encrusted with a thick layer of carbon, clean it using the brass bristle brush, then reinstall the plug.

    • 5). Examine the sparking electrode for any signs of physical deterioration such as pitting or burning. Stihl recommends replacing the spark plug whenever it is worn or no longer serviceable. If yours is badly worn or more than one year old, replace it with a new spark plug.


    • 1). Open the fuel tank and visually observe the condition of the fuel. If it has been many months since you last used your chainsaw, the ethanol-blended gasoline may have separated into layers and begun attracting water. Empty the fuel tank and fill it with fresh fuel.

    • 2). Note the power your saw develops when running. If the level seems low, you may have accidentally purchased 87-octane fuel instead of the minimum 89-octane fuel recommended by Stihl. Empty the fuel tank and replenish it with a higher octane gasoline and 2-cycle oil mixture.

    • 3). Examine the fuel pickup body inside the fuel tank, if it appears to be clogged with tiny bits of debris, remove it and clean it in a bath of pure gasoline. If it is badly discolored by contaminants, purchase a new unit from your authorized Stihl dealer and replace it.


    • 1). Remove the air filter cover and set it aside.

    • 2). Remove the air filter by sliding it upward out of the slots in which it rests.

    • 3). Examine the filter visually. If it is completely clogged with bits of sawdust, disassemble the unit and soak it in a bath of gasoline. When it is clean, set the parts in a sunny warm well-ventilated place to dry. If the filter is not terribly dirty, you can use compressed air to blow away any debris clogging the screens.

    • 4). Reinstall the air filter element and cover.

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