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OS140RX

Old 10-31-2006, 07:49 AM
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wingster
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Default OS140RX

I have a 140rx with about 100 flights on it. The motor runs good, but I have one problem.

I have been going through a glow plug(OS F) about every 15 flights since it was new. I don't think I am running lean.

I have been using 15% nitro, turning a 3 blade apc 15.75 x 10 prop at about 7700 RPM.

Any suggestions?
Old 10-31-2006, 11:29 AM
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Bax
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Default RE: OS140RX

Very likely, your engine may be detonating. 15% nitro is starting to get a bit high for a large engine, and with a 3-blade propeller, you may be very close to overloading the engine. We'd also use a #8 plug in that engine. You'll have to look at the plug to see what's going on. If the element is being broken and/or being bent, then it's certainly detonation. You may also be able to see a ring of discoloration on the piston that has its center line up with the plug.

If you're running a pipe, then it may not be tuned quite correctly. Tuned pipes can be hard on plugs, and it's not unusual for short plug life when tuned pipes are used. Pattern flyers will put new plugs in their engines before every contest, and before every critical flight.

If the engine's running well, otherwise, it may just be conditions. Check cooling, check the purity of your fuel, and so forth. If the engine's running well and not leaned, then the setup and type of flying you're doing is what's hard on the plug, and it may just be something you have to live with.
Old 11-07-2006, 11:00 AM
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wingster
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Default RE: OS140RX

Bill

I took the head off and did not find a ring of discoloration. The top of the piston did have a layer of thin dark sludge. Most of this wiped off easily but a thin dark layer is baked into the top of the piston in a few spots.

I also noticed a thin dark line running vertically along the cylinder liner. The line was about 1/32 " wide. It was especially pronounced at the top of the cylinder, not noticeable in the center, and very faint at the bottom. This was not a score line, but perhaps the result of the ring gap where wear did not occur.

I am running a tuned pipe, however this is a setup that many pattern fliers are using and have much better plug life. I will get a #8 plug and try that. Is adding an extra head gasket or two worth trying in order to reduce compression.
Old 11-08-2006, 12:35 PM
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Bax
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Default RE: OS140RX

You can add a gasket and see. That's the only way to find out if it will help.

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