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O.S. Engine After-Run Recommendations

Old 09-18-2009, 10:56 AM
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Default O.S. Engine After-Run Recommendations

We have seen some posts where individuals have complained that we do not honor the O.S. warranty, or that we try every trick possible to not honor the warranty. That is nothing further from the truth! The O.S. warranty covers repair or replacement, at our option, of actual defects in parts and workmanship of the original manufacture of the engine for a period of two years from the date of original purchase. We honor that to the letter!

We do see, however, many engines come in that have damage to them from corrosion, overheating, impact damage, and so on. If we see an engine with those difficulties, we inspect them carefully to see what the actual cause may have been. However, please be aware that damage from an overheat not specifically caused by the way O.S. made the engine, or damage from corrosion are not really warranty issues.

Overheating is rarely a defect in the engine, but many engine owners do not believe that. They think that once an engine's set, they can forget it...or once they've been told a temperature by a buddy or online article, that's it...or they've been given a set number of turns and they'll be OK. Setting an engine is unique to every installation, and will change from day-to-day. It must be set for each day's demands. An overheat will result in scoring of the piston, ring, and liner, and will cause the cylinder head bolts to become loose once the engine's cooled.

Corrosion is a byproduct of using glow fuels, especially high nitro fuels. The fuel, itself, will absorb moisture from the air, and combustion products will work their way into the engine's lower end. Those combustion products include water, some gasses, and a small amount of acid...nitric and nitrous acids. These combustion products can encourage corrosion development on the steel parts of the engine. Corrosion can be prevented by aggressive use of after-run oils that will displace the fuel residues and coat the steel parts of the engine. You can use specially-bottled after-run oil, red-colored automatic transmission fluid (Dextron II or equivalent), air-tool oil, a good-quality coating machine tooling oil, non-graphite gun oil, and such. If the fuel has an oil package which contains at least 50% castor oil and the total oil in the fuel exceeds 18%, you may be able to get by without after-run oil for short periods of time. In this instance, you'll need the after-run oil to prevent gumming of the castor oil and to prevent corrosion.

At the end of the flying day, disconnect the fuel line from the carburetor and run the engine at idle with the glow plug ignitor battery connected until the engine quits. Then make several attempts to start it until it will no longer fire. It will then be dry of fuel. You will not damage your engine running it in tis manner. Remove the glow plug battery connector. Open the throttle to full and inject a teaspoon or two of after-run oil into the carburetor air intake and turn the engine over by hand while you rotate it into a variety of positions. You may need to remove an air cleaner or other intake device to make access easier. A long, flexible tube on your oil can/bottle can help.

O.S. does state that you should not put a petroleum-based oil through the carburetor, but that refers to flowing it through the fuel passages. If you inject it through the carburetor air intake, you will be just fine. If you have a diaphragm pump on the engine, disconnect the pump line so that the oil does not damage the pump diaphragm.

You want to make sure the oil gets to the bearings. A few drops are useless, because there just won't be enough oil to do a good job of coating the internal parts. You cannot add too much after-run oil. If you have difficulty starting the first time at your next flying session, you've done a good job of coating the engine's internals.

We don't warranty engines from those users who ignore recommendations and choose to not take protective mesaures with their expensive equipment. Steel bearings, piston rings, liners, and bearing races all need oil to prevent corrosion between usage. Remove air filters at the end of each days running and inject oil directly into the open carb air intake. Use a starter to turn the engine over rapidly and disperse the oil throughout all engine parts. Just be careful that, if your engine is side-mounted or inverted, that you do not cause a hydraulic lock in the cylinder by allowing too much oil to build up in the cylinder.

Some fuels state that they have anti-corrosion products in them so you won't need after-run oil. We've never seen successful implementations of that. We strongly recommend the use of after-run oils in EVERY glow engine at the end of the day's flying."
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