RETURNING TWO-STROKE ENGINES TO SERVICE AFTER LONG - TERM STORAGE

Spring and the approach of warmer weather signal that it's time to get those flying machines out, and into shape for a new season. In a previous article, we explored the procedures needed to prepare two-stroke engines for winter storage. Now it's time to reverse the process, and get the engine ready to run and fly.

Before you even THINK about pulling that starter rope (or flipping the switch, if you have the convenience of electric start), several important steps must be taken to be sure that the engine is ready to crank up, and that this can be accomplished without causing serious internal damage. If you have done a good job on the pre-storage prepa- ration, reviving your power plant should go smoothly using the procedures described below.

The first order of business for an engine with electric start is to check out the battery. Visually inspect the case for any damage or electrolyte leaks. Also check the terminals for looseness or damage. Replace the battery if any such conditions exist. Put the battery on a long, slow charge (too quick and heavy a zap can fry it--take your time), then load test the battery. This can easily be done with an inexpensive tester available at most auto parts and department stores. Replace the battery if it fails to take or hold a charge. Clean terminals, check battery mounting hardware, securely remount and reconnect the battery.

Next, it may be necessary to undo a few things that were done prior to storage. If the engine was wrapped in protective material, such as plastic sheets, or the intake and exhaust were capped or sealed as recommended, these coverings will need to be removed. Check around intake and exhaust outlet to be sure that there is no foreign material that could enter the engine.

Now, clean away any dirt or dust around the spark plugs and remove all plugs. With the ignition switch off, rotate the engine by hand. With the spark plugs removed there is no compression. The engine should turn freely and easily by hand. If the engine turns hard, place about 1/2 ounce of two-stroke oil, of the type recommended for your engine, into each cylinder through the spark plug holes. Oil can also be sprayed or squirted into the intake while the engine is being turned. All of this should help to break up slight deposits of rust that may have built up in storage. The piston rings and cylinder walls are usually the worst culprits for this condition.

If the engine turns very hard, or is completely seized, DO NOT FORCE IT. Trying to force the engine to turn in this condition will almost certainly cause some damage. For example, you might crack a piston ring. This is a condition that may not show symptoms right away, but may come back to haunt you later on--like when you are airborne.

When a tight, or seized two-stroke is encountered, the best window into the cylinders is usually through the exhaust ports. Remove exhaust pipes, muffler and manifold and inspect cylinder walls, pistons and piston rings. Likewise, removal of air/fuel induction compon-ents lets you look into the crankcase and crankshaft area. Spraying or squirting two-stroke oil of the type recommended by the engine manu- facturer directly on pistons, cylinder walls, crankshaft and bearings, and CAREFULLY turning the engine by hand will, in some cases, eventually free up the engine. If this approach does not work, or inspection shows seriously worn or damaged internal parts, engine teardown and overhaul by a qualified engine repair technician is called for.

At this point, as long as the engine turns freely, its time for what might be called a "tune-up". A new set of spark plugs, properly gapped, is always a good idea, and a relatively small expense. This is also a good time for new air and fuel filters. These and other maintenance items will usually be discussed in your owner's or operator's manual, and will probably be included in a 50 or 100 hour inspection procedure. The maintenance schedule for a particular engine may call for additional proce- dures, such as retorqing cylinder head or crankcase bolts. In all situations, follow the service requirements and procedures spelled out in your owner's manual and/or service manual.

Our next concern is a most important one -- fuel and oil. If you have fuel or fuel/oil mixture that has been sitting in a tank or other container for 3 months or more, toss it out (in an environmentally correct and legal manner, of course). It is also advisable to avoid using two-stroke oil that has been sitting around for a long time, or in an open container. Make up a fresh batch of fuel/oil mixture, following the requirements listed in the owner's manual. Always observe common sense safety proce- dures when handling fuel, which is highly flammable and explosive. Also take precautions to keep fuel and fuel handling equipment clean and free from dirt, moisture and other contaminants. Remember that high-quality fuel and oil are a two-stroke's best friends, and cheap or contaminated fuel and oil are its worst enemies.

Liquid cooled engines will require a refill, and possibly other attention to the cooling system. Some engine manu- facturers may allow for water only in the cooling system when freezing condi-tions are not expected. Others may recommend a mixture including anti- freeze or anti-corrosion additives. Again, consult the owner's manual for recommendations for specific engines.

Now, at last, it's time for start-up, shake-down and final tuning. Remember that your fuel system has probably been dry for awhile, and priming using a squeeze bulb or boost pump will be needed. As the fuel system is being primed, carefully check all fuel lines, con- nections and fittings for leaks. Keep in mind all standard safety precautions when working around running engines. Eye protection and hearing protection are strongly recommended. Always be mindful of turning props and other rotating mechanisms. Be careful around hot exhaust and other hot engine parts. Run engines only in a well-ventilated area.

With the aircraft securely tied down, start the engine according to the manufacturer's recommended cold start procedure. Run the engine up to operating temperature, then perform any adjustments (such as carburetion, fuel injection, ignition timing) as instructed in the owner's manual or service manual. Continue to run the engine at various RPM's while still in tie-down. Watch the engine for any unusual shake or vibration. Listen to the engine for any strange noises, such as knocking, skipping or backfiring. Closely observe gauge readings for any abnormal conditions. Most owner's manuals and service manuals include troubleshooting sections to help in diagnosing and correcting such problems. If any questions or doubts remain as to the running condition of the engine, it is best to consult a trained professional engine technician, the engine dealer or factory technical assistance line.

Any beast abruptly awakened from hibernation may act a bit strangely. Your two-stroke is no exception. Following the start-up and set-up procedures described above, performed in tie-down, it is best to make a few high-speed taxi runs and short flights within gliding distance of the landing site to complete the shake-down. Again, engine performance and gauges must be closely monitored during this phase of operation. If any questionable circumstances crop up, put it on the ground, check it out and be sure that the problem is cured before going too far afield.

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.