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OS 50 SX dead sticks

Old 07-16-2003, 12:57 PM
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Default OS 50 SX dead sticks

The motor is new (maybe 7 flights), old one (less than 20 flights) had the same problem but was replaced by the place I purchased it. The motor will have a couple of good running flights and then the engine will lean out and die. Facts: fuel 10% nitro, 18% oils, needle valve is about 2.25 turns out, leaves a smoke trail when flying (except when it leans out in the last flight), stock muffler, stock glow plug, break in prop. Thanks
Old 07-16-2003, 01:32 PM
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Default OS 50 SX dead sticks

If an engine is leaning in flight, it's almost always not the engine, but something in the engine/mount/airframe/fuel system.

Vibration-induced fuel foaming is the most likely cause, but sometimes under-cooling causing an engine to quit and gives similar signs to leaning out.

You need to go over the entire system carefully to see what the problem might be. It's not necessarily a cut-and-dried answer.

We'd suggest putting the engine on a test fixture with the stock muffler, and with everything in the open and correctly-positioned. That way, you have the engine isolated. If it will run "all day" on the test stand, then you'll be sure it's not the engine, and you'll have to be doing detective work on the airframe, fuel system, and exhaust system.

One hint is that the engine will run OK for a few flights and then have something happen. This suggests that there's something in the entire system and not just the engine.

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