How to Service a Lawn Mower

Service your lawn mower annually by changing the oil, replacing the air filter and spark plug, sharpening the blade, and cleaning the deck to ensure reliable performance.

1. Cool Down and Disconnect First. Let the engine cool completely if recently used. Disconnect the spark plug wire for safety. Position the mower on a flat, level surface and engage the parking brake if equipped. Remove the grass catcher and any attachments.
2. Drain Old Oil, Add Fresh. Locate the oil drain plug underneath the mower or use the oil fill tube to drain. Run the engine for 2-3 minutes to warm the oil for easier draining. Remove the drain plug or tip the mower to drain old oil into a container. Replace the drain plug and refill with fresh oil according to your owner's manual specifications, typically SAE 30 or 10W-30.
3. Install Clean Air Filter. Remove the air filter cover by loosening the wing nut or clips. Take out the old air filter and inspect the housing for debris. Clean the housing with a damp cloth. Install the new air filter, ensuring it sits properly in the housing, then replace the cover securely.
4. Set Gap, Swap Spark Plug. Remove the spark plug wire and use a spark plug socket to unscrew the old plug. Check the gap on the new spark plug using a gap gauge - it should match your engine specifications, usually 0.030 inches. Thread the new plug in by hand first to avoid cross-threading, then tighten with the socket wrench until snug.
5. Sharpen or Replace Blade. Tip the mower on its side with the air filter facing up to prevent oil leakage. Use a block of wood to prevent the blade from turning and remove the blade bolt with a wrench. Inspect the blade for damage, excessive wear, or dullness. Either sharpen the blade with a file or grindstone, maintaining the original angle, or replace it entirely. Reinstall the blade, ensuring it's properly oriented.
6. Blast Away Grass Buildup. Scrape off built-up grass clippings and debris from under the deck using a putty knife or scraper. Spray the deck with a garden hose, avoiding the engine and electrical components. For stubborn buildup, use a stiff brush and mild detergent. Let the deck dry completely before storing.
7. Test All Systems Go. Inspect the fuel lines for cracks or leaks and replace if necessary. Clean debris from the cooling fins and around the engine. Check the drive belt for wear and proper tension. Lubricate any grease fittings according to your owner's manual. Test all safety features like the blade brake and safety switches.