Small Engines (Lawn Mowers, etc.): lawnmower, plastic milk jug, spark plug wire

Question
I need to know how to change the oil in my craftsman 4.5 horsepower 21 inch mulcher.  I also need to know how hard it is to change the blade.  

Answer
Dawn
To change the blade For just some minor touch up, there is no real need to remove the blade. For major grinding and balancing, removal will be needed. Removal will also be required to inspect for a damaged or sheared blade lock key and to replace it if necessary.
In either case: disconnect the spark plug wire and tie it safely away from the spark plug terminal (several inches minimum) or remove the spark plug entirely to prevent accidental starting.

If the nut holding the blade on is just on very tight, use a block of wood to prevent the blade from turning. Use a good quality socket wrench or box-end wrench of the correct size - an adjustable or even open-end wrench may not be enough. The nut usually unscrews counter-clockwise. However, check this out first! A careful inspection of the threads on the end of the crankshaft will reveal the direction. Or, determine the direction of rotation which will be designed to tighten, not loosen the blade. Most, if not all, single blade mowers rotate the blades clockwise as viewed from above which will therefore use a normal right-hand thread nut.

CAUTION: Make sure that if the wrench slips, your flesh will not contact the blade or other sharp sheet metal - liberal use of rags or newspapers is a good idea. Arrange your position and the mower so you are pulling towards you - this is a more stable controllable arrangement.

A oil change is pretty simple The oil change procedure is a lot simpler than for an automobile as everything is readily accessible and there is no oil filter to worry about.
You will need a funnel, low wide container or drain pan for the used oil, and a container like a plastic milk jug for temporary storage of the used oil for disposal.

Spread adequate newspaper on the ground to collect any drippings.

Run the mower for about 2 to 3 minutes to allow the oil to circulate and warm up so that it is less viscous and will flow more easily. Stop the mower and remove the spark plug wire.

If the fuel tank is less than about 1/3 full, then you will probably not have any problems, otherwise you will have to drain some gas or remove the fuel tank so that gas does not spill out of the breather hole in the cap.

If there is an oil drain plug, you can use this to drain the oil. However, it is usually more convenient to just turn the mower on its side, carburetor side up. This is usually acceptable for the short time that will be involved. Immediately check for any oil leakage - if there is any, we will need to avoid tipping the mower as much - look for the drain plug.

Wipe around the oil filler cap with a clean cloth or paper towel to remove the dirt and grime that has likely collected there. The oil filler will either be on or near the bottom of the engine or at the top of the shroud (Eager 1 type). If it is not right at the bottom, there will be a dipstick attached to it.

Place your wide mouthed drain pan under the oil filler cap and remove the cap. The oil will flow into your pan. Let it continue until the dripping stops - probably 10 minutes or so.

Set the mower upright on a level surface. Wipe any drips on the engine and deck up with a clean rag or paper towel.

Use the recommended oil for your engine. SAE30 is usually specified by the engine manufacturer but they will usually state that 10W-30 or 10W-40 (SG rating) are acceptable substitutes. These 'multi-weight' oils are widely available and inexpensive. Typical small engine oil capacity is just over 1/2 quart. Start low and incrementally add oil until just below full on the dipstick or at the top of the oil fill hole if there is no dipstick. DO NOT overfill. Give it time for the relatively viscous oil to find its way into the crankcase. Tipping the mower back and forth a bit will help this process.

Replace the filler cap. Wipe up any additional drips.

Replace the spark plug wire. Then, start and run the engine for a couple of minutes. Wait a few minutes, then recheck the level. Top it off if needed.

Transfer the used oil from your drain pan to the storage container and dispose of it in an environmentally safe manner.