Monday, April 13, 2009

Lawn Mower Tune Up

With Old Man Winter yielding to spring, the season of yard work is upon us. One of the universal lawn care jobs is mowing the grass. It would be wise to do a simple tune up before you bring your lawn mower out of the garage or shed were it was blissfully hibernating.

There are three basic lawn mower tune up tasks:
  1. Changing the oil
  2. Replacing the air filter
  3. Installing a new spark plug
A fourth maintenance item that is infrequently needed may be sharpening or replacing the blade. I will only be covering the three common tasks outlined above.

Since there are several different lawn mower engine manufacturers, and each manufacturer has multiple engine models, you may have to slightly modify the tools and parts needed from the ones used in this tutorial. However, all 4 cycle lawn mower engines are very similar, so the steps of the walkthrough should still be of value.

Tools and Materials Needed
  • 3/8" square drive or appropriate wrench/socket to remove oil drain plug (if equipped)
  • Catch pan for used oil
  • Small funnel
  • Appropriately sized wrench, large pliers or channel locks to remove old spark plug
  • Anti-Seize thread compound
  • Dialectic grease
  • Screwdriver and/or wrench to remove air filter
  • New air filter (consult your lawn mower manual for part number)
  • New Spark plug (consult your lawn mower manual for part number)
  • New engine oil (consult your lawn mower manual for type and amount of oil)

Procedure Summary
  • Drain the old engine oil into a catch pan
  • Pour new oil into the oil dip stick tube
  • Remove the old spark plug
  • Apply anti-seize to the threads of the new spark plug and install it
  • Apply dialectic grease to the inside of the spark plug boot and install it
  • Remove the air filter housing and the old air filter
  • Clean the housing and install a new air filter
  • Reinstall the air filter housing onto the engine
Step 1
Pull the spark plug wire boot off of the spark plug. The spark plug should be mounted in the front of the engine. This will insure that by no means the engine can accidentally start and turn the blade while you are working underneath the lawn mower.

Step 2
If your lawn mower is equipped with an engine oil drain plug, tip the mower on its side to access the plug. It is helpful if the gas tank is empty. If you are not sure if your lawn mower has an oil drain plug, tip it on its side and look at the bottom of the mower. You should see a ring of bolts, these attach the engine to the mower body and are not drain plugs. If there is a single plug, probably with a square hole in it that a 3/8" drive socket fits, this is most likely the drain plug.
If the lawn mower does not have an oil drain plug, remove the oil dipstick and slowly turn the lawn mower over so the oil drains into the catch pan, then skip to step 4.

Step 3
This step helps if the mower is on higher ground than the catch pan. A simple way is placing the catch pan in the street and having the mower on the curb above it and some bricks, lumber, or anything else on the other side of the catch pan.
With the catch pan in place and the mower on its side, loosen the drain plug (1). Before the plug is about to come out, slowly return the mower half way to it upright position so that you can still reach the drain plug underneath the mower, but the plug is over the catch pan (2). Remove the drain plug and lower the mower so it straddles the catch pan (3). It will probably help the oil drain faster if you remove the oil dipstick from the top of the engine.

Step 4
Let the all the old oil drain out, then replace the drain plug (if equipped) or return the mower to its upright position.

Step 5
Place a small funnel in the oil dipstick tube and slowly pour the correct amount of new oil into it. When the correct amount of oil has been used, secure the tube with the dipstick - the oil change is done!

Step 6
Use a wrench, large pliers, or channel locks to remove the old spark plug.

Step 7
Apply a little anti-seize compound (found at auto stores) to the threads of the spark plug. Then, install the spark plug.
Step 8
Apply a bit of dialectic grease (found at auto stores) to the inside of the spark plug boot. Push the boot over the end of the spark plug until it seats itself - the spark plug change is done!
Step 9
Remove the air filter housing by removing a screw, bolt, or any fastener that holds it.

Step 10
Remove the old air filter and, if necessary, clean the inside of the air filter housing.

Step 11
Install the new air filter into the housing, and then install the housing to the engine - the air filter change is done!

Always remember to properly dispose of used engine oil. Most auto parts stores will recycle the oil free of charge as well as some recycling centers.

With that simple tune up, your lawn mower should be ready for another season of cutting the grass!

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