Do you just park your lawn mower or string trimmer in the shed at the end of the season and hope it will start next spring?
If so, you probably have experienced problems in getting the machine to run after storage. There are some simple steps you can take before storage to make your equipment easier to start when you need it again.
Change the Oil
The first thing you should do to prepare any 4-stroke engine for storage is to change the oil and oil filter. Drain the old oil. If you do this when the engine is warm, the oil will flow better and will be more likely to have any solids in suspension so the dirt can be removed with the oil. If the machine has an oil filter, replace it while changing oil. Measure in the recommended amount of the recommended quality and viscosity of oil, then check the oil level to be sure you have the right amount.
Inspect Spark Plug(s)
This is the best time to inspect spark plug(s) and service or replace them. If the plug tip or electrode is worn or burned, replace the plug. If the plug is covered with soot, oil or a white deposit, it should be cleaned and regapped or replaced. Check your operator’s manual for the correct plug gap, and use a plug gap tool to regap the plug (or to gap new plugs). Also check the operator’s manual for the correct spark plug torque and use a torque wrench to reinstall the plug (Figure 1). Many small engine heads are made of aluminum, and the threads can be easily stripped if the spark plug is overtightened.
It is helpful to squirt a teaspoon or less of oil into the spark plug hole while the plug is out, then turn the engine over a time or two (with the plug out) to lubricate the top of the cylinder. Expect a puff of smoke from the oil when you first start the engine in the spring. Do not add more than about a teaspoon of oil; too much liquid in the cylinder can cause severe engine damage on startup since liquids are incompressible.
Clean the Engine
You should clean the engine prior to storage. Most small engines are air-cooled. They have cooling fins on the engine block (Figure 2). These fins must be kept clean to avoid overheating the engine. It may be necessary to remove some of the engine shrouding to clean the cooling fins. Compressed air is the best way to clean the fins.
Inspect Air Filter and Fuel Filter
This is a good time to inspect the air and fuel filters and replace them if needed (Figure 3).
The volatile components of gasoline evaporate over time. Old gasoline will make your engine difficult or impossible to start in the spring. Probably the best way to avoid this problem is to run the engine dry before storage. Plan ahead, and don’t put in any more fuel than is needed for your last use, then run the engine dry when you finish using it. This will prevent both "stale" gasoline in the fuel tank and "varnish" buildup in the carburetor from evaporating gasoline. If you then fill up the tank with fresh gasoline in the spring, it should start readily.
An alternative approach is to fill the fuel tank at the end of the season with fresh gasoline to which a gasoline stabilizer has been added. You must add the stabilizer to fresh gasoline. The stabilizer can only stop deterioration; it can’t reverse it. It is best to add the stabilizer to a gallon (or more) of fuel in a storage can since it is easier to obtain the correct rate that way rather than trying to figure out how much to add to a small tank. Storing an engine with stabilized gasoline in the tank will prevent the problem of seals drying out.
Using Extra Gasoline
If you have gasoline left at the end of the season, it is best to use it in some other machine (or a vehicle) rather than keeping it over the winter. Gasoline mixed for a 2-stroke engine shouldn’t be used in most 4-cycle engines (and especially not in a vehicle with a catalytic converter). If you must store gasoline, be sure to add a stabilizer while it is still fresh.
A little maintenance and preparation in the fall can make a small engine much easier to start next spring. The most important step to easy starting in the spring is to avoid having stale gasoline in the tank.