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HelicopterHIROBOOther › Glow Plug
10-09-2017 08:29 AM  65 days agoPost 1
Mputu

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Killeen, TX

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Can anyone tell me what can cause this on the plug? that's a OS#8 just in case one wants to know. The plug is working.

Fly hard, Land safe

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10-09-2017 11:07 AM  65 days agoPost 2
dgoss999

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UK - Lancashire

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Possibly the crank bearings wearing or breaking up or crap ingested through the carb intake.. How many plugs have you had like this in this engine?

"Believe none of what you hear, and only half of what you see." • Benjamin Franklin

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10-09-2017 11:07 AM  65 days agoPost 3
wjvail

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Meridian, Mississippi

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I can't say for certain what causes it but I tell you it is very common. My guess is that there is a temperature difference where the plug element meets the plug body and it causes some coating of the element.

My guess is that most of the element runs hot enough to prevent this plating but the element cools enough near the plug body to allow some part of the fuel to plate the coil.

The other option is that because the plating is usually confined to the first turn of the element, where the element is most exposed to combustion and raw fuel, this is where the bulk of the catalytic reaction is occurring and some part of the fuel is deposited on the element in the process.

Whatever is causing it, this portion of the plug appears to be critical to good running. Build up on the first coil will cause poor running regardless of what the rest of the element looks like.

The good news is that very often it can be removed and the plug will function as new. It has a glass like quality that seems to insulate the element. It is very brittle, like glass, and is typically easy to remove. Generally a little work with the tip of a new #11 blade will completely remove the problem. You will likely find the element bright and shinny under the deposits.

If you don't mind me asking, what type of fuel do you use?

"Well, Nothing bad can happen now."

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10-09-2017 11:10 AM  65 days agoPost 4
JuanRodriguez

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The Villages, Florida

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The “frosty” condition on the element would indicate a lean running motor.....the blob looks like molten metal..... maybe the rear bearing starting to fail ???

Been there, done that and old enough to know better.....

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10-09-2017 12:10 PM  65 days agoPost 5
dgoss999

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UK - Lancashire

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I use a home brew - Methanol/ML70/nitro. As I first suggested, check your Crank Bearings, you should be able to feel if they are running rough.

Any roughness in the bearings, they should be replaced.

DG

"Believe none of what you hear, and only half of what you see." • Benjamin Franklin

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10-09-2017 04:14 PM  65 days agoPost 6
Mputu

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Killeen, TX

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wjvail
If you don't mind me asking, what type of fuel do you use?
I used three different fuel so far, Coolpower, Wildcat, RotorRage, and Home brew as well.. for this plug it was Wildcat and Homebrew.

Fly hard, Land safe

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10-09-2017 04:16 PM  65 days agoPost 7
dgoss999

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UK - Lancashire

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Check your bearings....

DG

"Believe none of what you hear, and only half of what you see." • Benjamin Franklin

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10-09-2017 04:17 PM  65 days agoPost 8
Mputu

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Killeen, TX

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dgoss999
I use a home brew - Methanol/ML70/nitro. As I first suggested, check your Crank Bearings, you should be able to feel if they are running rough.

Any roughness in the bearings, they should be replaced.
Well, I have to check this one out, however, this is a brand new engine, and I am running it rich as you can see on the plug.

Fly hard, Land safe

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10-09-2017 04:19 PM  65 days agoPost 9
dgoss999

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UK - Lancashire

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Unless there is much 'running in' debris floating about.. I have no more suggestions I am afraid..

DG.

"Believe none of what you hear, and only half of what you see." • Benjamin Franklin

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10-09-2017 04:20 PM  65 days agoPost 10
Mputu

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Killeen, TX

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The “frosty” condition on the element would indicate a lean running motor.....the blob looks like molten metal..... maybe the rear bearing starting to fail ???
Maybe ocasionnal lean, but for the most part this engine is running rich, will check the rear bearing as well.

Fly hard, Land safe

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10-09-2017 04:20 PM  65 days agoPost 11
JuanRodriguez

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The Villages, Florida

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Mputu
Well, I have to check this one out, however, this is a brand new engine, and I am running it rich as you can see on the plug.
As I stated above, the frosty appearance on the plug element indicates lean running motor, not rich !!

Been there, done that and old enough to know better.....

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10-09-2017 04:26 PM  65 days agoPost 12
Mputu

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Killeen, TX

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I discovered this by curiosity, you will not be able to see this just by looking with naked eye. I used a magnify lens to look thru inside the plug just by curiosity, I have three plugs like that from four different engines. two of them I have to rebuild anyway.

Fly hard, Land safe

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10-09-2017 04:32 PM  65 days agoPost 13
Mputu

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Killeen, TX

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JuanRodriguez
As I stated above, the frosty appearance on the plug element indicates lean running motor, not rich !!
Rod, I am not disagreeing with you, I used a flash while taking this picture last night, I just think that the picture alone with the frost is the result of the poor lighting using a flash.

Fly hard, Land safe

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10-09-2017 04:38 PM  65 days agoPost 14
JuanRodriguez

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The Villages, Florida

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Ok..... a “normal” looking element should not be significantly different from that of a new one.... fairly shiny and without distortion.....

Been there, done that and old enough to know better.....

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10-09-2017 04:49 PM  65 days agoPost 15
wjvail

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Meridian, Mississippi

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Mputu... for the most part your plug looks normal. It just looks like it been run a lot. The black booger that forms is very typical and the dull gray is an indication that a plug has been run fairly hard but not overly so. While I too mix my own fuel, I have seen the same deposits when using commercially blended fuels.

I'm sorry to disagree but bearing failures do NOT look like this. I fact, they look just the opposite. Typically a bearing failure looks like mechanical damage to the element (pitted, bent or broken) and they often look particularly clean - as if they have been blasted by a particulate. Often what fails in a rear bearing is the cage and it can leave a brass looking deposit on the parts of the plug exposed to the combustion chamber.

2 minutes ago I removed the OS #8 from my 55 Hyper. See attached photo.

"Well, Nothing bad can happen now."

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10-09-2017 05:07 PM  65 days agoPost 16
wjvail

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Meridian, Mississippi

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For example purposes I just pulled the very old plug out of my RCV 58CD. While this is a very unique engine, the plug doesn't look much different than the one you posted.

"Well, Nothing bad can happen now."

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10-09-2017 05:10 PM  65 days agoPost 17
payne1967

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uk

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how do you seal your exhaust?
is the blob some epoxy/silicone or similar sealant?

www.alcesterhelicopterclub.bmfa.org

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10-09-2017 05:19 PM  65 days agoPost 18
wjvail

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Meridian, Mississippi

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As I mentioned before, often the black deposit can be removed with a gentle touch of an Xacto and the plug will be fine. This pic is from the same plug in the last post.

"Well, Nothing bad can happen now."

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10-09-2017 05:44 PM  65 days agoPost 19
Mputu

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Killeen, TX

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payne1967
how do you seal your exhaust?
is the blob some epoxy/silicone or similar sealant?
I don't use any epoxy or silicone base at all. just use the aluminum or copper seal that came with the muffler.

Fly hard, Land safe

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10-09-2017 05:49 PM  65 days agoPost 20
Mputu

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Killeen, TX

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wjvail
As I mentioned before, often the black deposit can be removed with a gentle touch of an Xacto and the plug will be fine. This pic is from the plug in the last post.

WJVAIL,

Thank you for the enlightenment, now I know there is nothing wrong with the engine nor bearings. The plug I posted was from the OS 55 but the one from OS91 and OS105 all looked the same.

Fly hard, Land safe

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