Model Engine Company of America
How to break in a Ringed Engine

A Ringed engine requires more break in than an ABC engine and in turn usually lasts longer and takes more abuse than an ABC engine.

The ring, which is usually made of an iron alloy must be mated to the hardened steel cylinder liner. The mating surfaces of the ring and cylinder must be perfect to create the proper seal. Many other factors are important too, like the piston fit and the quality of the ring and groove as well as the finish in the cylinder bore. If anything is not made correctly no amount of break in will correct the problem. NOTE: Dykes type rings feel different than conventional rings. Click to learn the difference.

A model engine makes sounds that will tell you how it's performing. You'll have to listen very carefully for them, recognize their message, and make adjustments to the fuel control needle valves accordingly. The mixture of fuel and air is controlled by the amount of fuel metered by the needle valve.

SLOPPY RICH MIXTURE running is characterized by a very slow, irregular, sputtering exhaust sound. The exhaust gas will be very smoky and contain many droplets of oil. This condition is good for the very first initial run of a ringed or lapped engine as it receives excess lubrication and runs cooler.

RICH MIXTURE running is characterized by a slower, sometimes irregular, sputtering exhaust sound. The exhaust gas will be smoky and probably contain small droplets of oil. This condition is good for Break-in since the engine receives excess lubrication and runs cooler.

FOUR CYCLING or SLIGHTLY RICH is a rich type setting, but it is fast enough to pull the airplane. This is the setting you normally look for before launching the airplane because the engine will run leaner when airborne.

PEAKED OR TWO CYCLE. As the main needle is closed (clockwise), it reduces the amount of fuel mixed with the air drawn into the engine. At a specific point, which varies with each engine, air temperature, altitude and relative humidity, the exhaust note will change quickly into a smooth, powerful note. If the needle is closed further, the note will stay smooth, but will weaken. The peak occurs just at the break point from a rich setting and further leaning will ruin the engine. A lean setting raises the engine heat above the safe point, reduces lubrication, and destroys glow plugs due to high combustion temperature. This is very harmful to the engine and your investment. Learn to tune the engine before flying. Remember, a little rich is always preferred for long motor life.



The initial bench break-in period is approximately 90 minutes (40 to 45 minutes bench and 45 minutes airborne). During this time, use the recommended break-in propeller and run the engine at a rich setting. It is best to run the engine for about 10 minutes, then allow it to cool. The heating and cooling aid break-in on a ringed type engine.

1> Start the engine and run it at a rich full throttle for about 1-1/2 minutes, then let it fast idle (about 3500 rpm's) for 30 seconds. Repeat this sequence for about 20 minutes of running time.

2> Increase the full open throttle time to about 3 minutes followed by a 30 second idling period. Do this for an additional for 20 minutes.

3> Install the engine in your aircraft. Using an normal size prop, proceed as described in step 2 of "AIRBORNE BREAK-IN".


1> BREAK-IN running should be done with the recommended propeller at a rich setting. The needle valve should be set at a point just into this range from a four cycle setting. Fly the plane at maximum throttle for 2 minutes, then throttle back for approximately 30 seconds. Repeat this sequence until approximately 45 minutes of accumulated running time has been obtained. Additionally, certain maneuvers, such as "CUBAN EIGHT'S", that allow the engine to load and unload are recommended. AVOID PROLONGED CLIMBING MANEUVERS AT MAXIMUM THROTTLE.

2> After the first 45 minutes change to normal size prop and fly an additional 45 minutes. Continue to run the engine at a slightly rich four cycle setting and fly your normal pattern.

3> After the above break-in period, run the engine at a normal peak needle valve setting. This should be a little on the rich side because engines run leaner in the air. 5% - 15% nitro may be used.

The above information is provided as a guide. Since MECOA/K&B has no way of determining the ability of the individual using and understanding this information, we assume absolutely NO RESPONSIBILITY for any damage to person or property from the use of this information.