End of Season Lawn Mower Maintenance

Here is what you should do at the end of the mowing season:

  • Change the oil. If you do nothing else in this list, at least change the oil. Old dirty oil will shorten the life of your engine and affect its starting and running performance eventually.

  • Drain the fuel tank (see the section: Gasoline for tips on doing this). Put this and any fresh (unmixed) gas remaining in your gas supply can into your car's fuel tank (preferably at least half full to dilute it) so you won't be tempted to use it next season. Or, discard it in an environmentally friendly manner. Then run the mower until it stops from lack of gas which will use up the gas still remaining in the carburetor (at most a couple of minutes). Purging the engine of old gasoline is particularly important for float type carburetors. Otherwise, evaporation and oxidation may result in the formation of insoluble gum which will eventually clog up your carburetor.

    Also see the section: Additional comments on winterizing - draining versus the use of fuel a stabilizer. The use of stabilizer is convenient but I think draining is preferred as it is safer not storing garden equipment over the winter loaded with gasoline.

  • Inspect the air filter (and fuel filter if present). If dirty or clogged, clean or replace as appropriate.

  • Remove and inspect the spark plug. The curved electrode and tip should be smooth and light gray or brown in appearance. If they have deteriorated or are damaged in any way, replace the spark plug. Engine repair books usually recommend replacing the plug in any case - they are inexpensive, under $2. Use the proper small engine spark plug - not one you found in the corner of your toolbox or removed from your automobile! A bad spark plug is a major cause of a hard-to-start engine. Check the spark plug gap (new or used) with a feeler gauge - it should be .030" for most small engines. Carefully bend the curved electrode to adjust - do not file the center electrode!

  • Squirt a teaspoon or so of fresh engine oil into the spark plug hole so that it coats all sides of the cylinder. WD40 will work as well since its purpose is protection and not lubrication. Then crank the engine a couple of times to distribute it. The oil will protect the cast iron cylinder liner and piston rings from rust during the off-season.

  • If you reinstall the old plug, it is generally good practice to replace the metal washer. Install the spark plug finger tight and then tighten another 1/2 to 3/4 turn or to 15 to 30 ft-lbs with a torque wrench using the proper deep (spark plug) socket.

  • Clean above and below deck to remove dirt, leaves, and other debris. Pay particular attention to the area around the cylinder under the shroud (blower housing). Remove any leaves or other debris that might impede the all important air flow.

  • While underneath, inspect the blade for serious damage that would require resharpening or replacement. It doesn't have to be honed like a scalpel but there should not be too many deep nicks and it should not wobble noticeably or be bent or have bent or distorted tips.

  • If you have a battery for electric start, make sure the water reservoir (if not the maintenance-free type) is topped off, the terminals are clean and tight, and that it is fully charged.

  • Put a light coating of oil on any exposed unpainted steel parts. Check any front wheel drive components - chains, idlers, pulleys, and clean and lubricate if necessary. Dribble a few drops of light oil into any throttle, choke, safety interlock, or other cables.

  • Store the mower in a dry location supported off of the floor on wood blocks if there is any chance of flooding.

Then, when it comes time to start mowing again (yes, I know, you can't wait), all you should have to do is add fresh gas (don't use last season's). The mower should start on the first (well, maybe, second) pull. There may be some white/blue smoke for a few seconds from it burning off the oil coating on the cylinder walls but this should quickly disappear.

The Lawn-mower-shop.com Web site has great deal of useful information including diagrams of popular carburetors and links to small engine manufacturers.

Here is another recommendation:

(From: Bill Harnell ([email protected]).)

Change the oil at the *end* of the season. No need to leave the acid charged oil in the crankcase over the winter to corrode the engine.

Then add a couple of teaspoons or so of Stabilit to the gas tank. Run the engine for approximately 5 minutes and while you're at it, inject some fogging oil through the carburetor to thoroughly coat all of the interior surfaces. Directions are provided on the fogging oil container.

Wipe the frame and handle with an oily cloth and oil all pivot points lightly. Clean the crud from under the deck - you do that frequently all summer - right? Remove all the grass clippings from around the flywheel and the cylinder fins.

Then store it in the shed or garage.

It will start on the first or second pull every spring.

BTW, you should be able to get both Stabilit and fogging oil at any reputable engine service center.