PREPARING TWO-STROKE ENGINES FOR LONG-TERM STORAGE

As winter closes in and it's getting a bit chilly to be flying about in an open or unheated cockpit, most ultralight owners reluctantly hangar their aircraft. The cold months are then spent dreaming of spring and favorable flying weather. As a new flying season approaches, the last thing one should have to deal with is major engine problems. A few simple steps now, as the aircraft is being prepared for storage, will go a long way in preventing such problems, which could cause delays in getting back out and up, and the need for costly repairs.

Long-term storage can have several negative effects on a two-stroke engine. In calculating fuel/oil ratios for normal running conditions, two-stroke engine manufacturers generally keep the mixture as "thin" as practical while still maintaining adequate lubrication. This, of course, is to minimize undesirable situations such as gummy piston rings, fouled plugs and excessive exhaust smoke. If an engine was simply shut down and stored after running on the "normal" fuel/oil mixture, the lubricating oil film left behind would not be adequate to protect internal parts for long periods of time. When a two-stroke engine is shut down, pistons may stop in a position in which exhaust ports are uncovered and the cylinders are wide open to outside air. Air can also enter the crankcase through induction ports. Fluctuations in temperature and humidity can result in a considerable buildup of condensed moisture throughout the interior of the engine. The resulting rust and corrosion can seriously damage internal parts and cause the engine to become seized tight. This situation can occur after only a month or two out of service.

When gasoline is left in a tank, carburetor, fuel injection unit or fuel lines, the volatile fractions evaporate rapidly, leaving behind the heavier fractions which form gummy varnish deposits. These deposits can easily plug carb passages and injector components, necessitating the time-consuming process of disassembly and de-gunking. Fuel stored for long periods of time in a typical 5 to 6 gallon "gas can" is also subjected to this de-terioration. Stale fuel can cause many problems affecting both the perform- ance and the longevity of the engine.

Liquid cooled engines require additional care in preparation for storage. If water alone is used as a coolant, and this were to be left in an engine under freezing conditions, severe damage to the engine will occur. This can include warped and cracked crankcase, cylinders and cylinder heads. Radiators and other cooling system components can also be damaged. Aluminum alloy engine components are subject to corrosion, even when a liquid coolant mix includes antifreeze or other corrosion inhibitors. These additives break down after a period of time, so used coolant left in the engine may not prevent this problem.

While the potential problems of long-term engine storage are many, prevention is a matter of a few simple steps. Safety is the first priority. Remember that fuels and their vapors are extremely flammable and even explosive. Fuel should always be handled in a well-ventilated area, and must be stored and transferred only in approved containers. Do not smoke or handle fuels near sources of heat or flame. Be careful when working around rotating components and hot engine parts. Environmental concerns should also be kept in mind. Fluids such as old fuel and used coolant must be disposed of in accordance with applicable government regulations.

Listed below are the steps for long-term engine storage recommended for engines manufactured by 2 Stroke International, including our AMW and Cuyuna engine lines. Procedures for engines built by other manufacturers may be similar, however, it is always good practice to consult the Owner's Manual or other service literature that applies to your specific engine.

1. Run engine until warmed up to normal operating temperature, shut engine off.
2. Close fuel manual shutoff valve(s), or turn tank switching controls to the off position.
3. Remove air cleaner(s).
4. Restart engine and run at idle speed. As the engine begins to break up due to "running out" of fuel, use pump oiler or other appropriate device to inject clean two-stroke oil (as specified by the manu- facturer) rapidly into the air intake(s) for 10 to 20 seconds until the engine stalls. This will coat crank- shaft and bearings with oil, and clear out fuel lines and other fuel system components.
5. Install tight-fitting sealing plugs over air intake(s), or reinstall air clean- er(s) and wrap tightly with plastic bag(s).
6. Remove spark plugs. Pump ap- proximately 1 oz. (30 ml) of clean two-stroke oil into each cylinder. With ignition OFF, slowly turn the engine two revolutions BY HAND, to distribute oil over pistons, rings and cylinder walls. For inverted engines remove only one spark plug per cylinder, inject oil while turning engine. Quickly reinstall spark plugs. Special spark plug replacements containing desiccant crystals can be used to absorb moisture from the cylinder and combustion chamber during long-term storage.
7. Install tight-fitting sealing plugs or plastic bags over exhaust outlet(s), after exhaust has cooled.
8. For liquid cooled engines, drain the entire cooling system, after engine has cooled. Close drain valve(s), tightly reinstall pressure cap.
9. Drain all fuel from tank(s), fuel lines, fuel filters, gascolaters and other fuel supply system compon- ents. Close manual drain and shutoff valves. Reinstall fuel filler cap tightly. Seal fuel tank vent(s) with appropriate plug seals to prevent moisture from entering tank(s).
10. On float carburetor engines, re- move float bowls and drain fuel. Reinstall bowls.
11. Disconnect and remove the battery (if so equipped) for storage outside and away from the aircraft.
12. Store the aircraft in a dry, protected area and/or wrap the entire engine in plastic. When practical, dismount the engine and store separately in a dry, protected location.

Equally important is the procedure for preparing the engine to be returned to service after long-term storage. This subject is covered in an article entitled Returning 2 Stroke Engines to Service Following Long-Term Storage. Refer to this article to get your engine and aircraft ready for spring, and a new and exciting sport flying season.

Reese Griffin is in charge of Technical Publications for 2 Stroke International (2si) in Beaufort, SC. 2si is a manu-facturer of high-performance, light-weight engines ranging from 7 to 100+ horsepower. 2si engines are used by many ultralight and kit plane builders, as well as in numerous other aviation and non-aviation applications.

A free information packet is available by contacting 2 Stroke International, or the Authorized Dealer at the address below.