Lawn mowers need routine maintenance. Several experts recommend:
If you didn't clean the mower before storing it last fall, give it a good cleaning now. Remove the spark plug to prevent accidental starting, then clean the outside body and handles with mild soap.
Use a paint scraper to remove any residue from grass clippings underneath the mower. Some owners will spray the undercarriage with nonstick cooking spray to prevent buildup.
While cleaning, tighten all screws and bolts and make sure all switches, levers, pulleys, etc. move properly.
Sharpen the blades at the beginning of the season and after every 25 hours of use.
Replace the spark plug at the beginning of each season.
Check the fuel and oil levels before each use, and change the oil at least once each season. Make sure the engine has cooled down at least 10 minutes before refueling.
Clean or change the air filter and lubricate the wheels and moving joints after every 25 hours of use.
Always check the owner's manual for the recommended parts, oil, filters and fuel for your mower.
Sources: www.Bladepro.com and www.Learn2.com