I''m a long time fan of OS MAx engines (since 1978 !) and have purchased numerous different sizes over the years and have had very few problems - I always reccommend OS to fellow modelers. I recently purchsed a new .91FX from Tower on 1/05/08. I installed the engine and have startyed flying it and have only approx 1/2 gallon of Byron 15% (18% oil) glow fuel through it. I ALWAYs run it dry before storage and use after run oil religiously and plug the exhaust and intake. It''s never been in wet conditions such as rain, etc....Also, I live in southern AZ so the humidity is natually low here.

I recently noticed that the engine felt "rough" and suspected a bearing issue. Out of curiosity I disassembled the engine and was shocked to see lots of rust. The rear bearing is very rough feeling when spun. I cant image that the rust developed due to improper maintenance on my part based on my post-flight regime. I''m thinking that it existed prior to my purchase and worstened in spite of my post-flight care but do not have evidence of that.

I also had a similar situation with a new .46AX....same looking rust deposits after only a few months. At this point I''ll be pulling the backplates to check for rust after delivery.

Have you been seeing many new OS engines experiencing bearing issues lately ?

I cant think of anything I can change on my side. Suggestions ?

Thanks, Eric

We''ve never seen corrosion on new, unused engines. Corrosion almost always starts the first time an engine is run. The fuel we use attracts moisture, and combustion products do work their way into the lower-end of the engine. The combustion products are mildly corrosive. When you put them into an engine, you have a mild electrolytic solution, that combined with the dissimilar metals in the engine, will cause corrosion.

Higher-nitro fuels will give you slightly-more acidic combustion products, so you need to be more proactive when nitro starts getting above 15%-20%.

To prevent corrosion, you need to use a model fuel that is heavy on castor oil in the oil mix, or use a good-quality after-run product. A good after-run oil would be red automatic transmission fluid, air-tool oil, non-graphite gun oil, or any of the commercial products sold as after-run products. Be very, very liberal in your application of after-run oil. A few drops are worthless. You need to make sure that the bearings and crankshaft are well-coated. The larger the engine, the more oil you''ll need. Four-stroke engines need the oil injected into the crankcase because oil put into the carb won''t coat the lower-end. Don''t put the oil into the fuel nipple of the carb of any engine, but put it into the air passage in two strokes, or into the crankcase vent nipple in four-strokes.

BAX,
I''M RUNNING MORGAN COOL POWER 15% WITH 4 TO 6 OZ OF KLOTZ CASTER OIL ADDED PER GALLON FOR ADDED PROTECTION. MORGAN FUEL DOES "NOT" WANT US TO USE AFTER RUN OIL. WILL MY ENGINES BE OK??? I HAVE OS, TOWER, THUNDER TIGER ENGINES SOME 16 OF THEM FROM .46 TO 1.20 SIZE. NO PROPLEMS SO FAR. STORED IN HEATED GARAGE WHEN NOT IN USE. SHOULD I BE USING AFTER RUN OIL? richgrow

With ANY glow fuel, we''d recommend after-run oil. It will cut castor oil a bit and help prevent it from becoming gummy, and will lubricate the parts in non-castor fuels. Some fuel manufacturers state that they have a rust preventative, but it only slows down corrosion a bit and cannot prevent it...they can''t put enough of the stuff in their fuel and still give you a good-running engine. We apply after-run oil to every glow engine we run in the shop.