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  1. #1

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    Raptor 50 Engine Piston has black spots

    Hi,
    since about a week ago my raptor engine was not behaving the way I'm used to. I've been flying this engine for many years now without a problem. So when I took it apart I noticed this black "stuff" on the surface of the piston. The engine is the ordinary engine that comes with the raptor. The black stuff was also on the glow plug although I just recently replaced it. I wonder if the "black stuff" is an indication of the engine being to lean or too rich or just simply too old. Any help is greatly appreciated.
    Best,
    Dirk
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  2. #2
    Moderator BarracudaHockey's Avatar
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    RE: Raptor 50 Engine Piston has black spots

    Hard to tell but it looks hot, is that acually pitted into the top of the piston or is it something accumulated on the top that you can scratch off?

    If its pittted, it looks like the bearing is coming apart.
    Andy - Helicopter Forum Moderator
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  3. #3

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    RE: Raptor 50 Engine Piston has black spots

    Hi,
    thanks for the response. I can wipe this off with my fingers. It comes of relatively easy. The surface underneath is fine.
    When I flew a couple of weeks ago the engine stalled on me for the first time during hover. Luckily I was able to land safely.
    If you have another idea what this could be please let me know. The engine has run approximately 10-15 gallons so far.
    Best,
    Dirk

  4. #4
    krisma's Avatar
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    RE: Raptor 50 Engine Piston has black spots

    Do you have an air filter in place?: filter degrading. Have you recently changed to a new brand/different ratio gas? Using old gas? Recently purchased a new gallon of gas? Changed type/brand of glow plug recently?

  5. #5

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    RE: Raptor 50 Engine Piston has black spots

    I don't have an air filter and use the same type of plug and the same type of gasoline.
    However the gas might be a bit old. I didn't fly for 2 months or so and the
    gas container was opened about 4 months ago I guess. Is that old? What the expiration date for
    the nitro? What could it be if the gasoline is too old?
    Thanks Dirk

  6. #6
    Charlie's Avatar
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    RE: Raptor 50 Engine Piston has black spots

    However the gas might be a bit old. I didn't fly for 2 months or so and the
    gas container was opened about 4 months ago I guess. Is that old?
    I've used fuel 2 years old in my helis and never had a problem. I had some real old heli fuel one time (about 1/2 gallon 6 years old) I didn't
    want to put it in my heli so I burnt it in my little car and it worked great (I was very surprised).

    I guess it boils down to how you store it, I keep mine stored in a dark cool place.
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  7. #7
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    RE: Raptor 50 Engine Piston has black spots

    Here are a few things to consider based on my experience:

    1. I have owned several nitro helicopters and one gasoline-burning helicopter. NONE of them has ever had an air filter. Unless you fly in REALLY dusty places, and spend a lot of time close to the ground, it is not needed.

    2. I buy my fuel in bulk. My current stash was purchased about 4 years ago. Since I fly airplanes and helicopters, I keep 2 bottles of fuel opened in my flight box. Of course, the heli fuel gets used up a lot faster than the airplane fuel, but the airplane fuel has been there for a good 6 months. I have no issues with that fuel.

    One thing that you failed to mention is the brand and composition of your fuel. This might help pinpoint the problem.

    Rafael
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  8. #8

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    RE: Raptor 50 Engine Piston has black spots

    I'm using Cool Power with 15% Nitro. I read somewhere that it might be the muffler that causes this, e.g. the material is being
    pushed back into the cylinder.....

  9. #9

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    RE: Raptor 50 Engine Piston has black spots

    Looks like carbon?? burnt oil and fuel will create carbon. same as on a real car engine. same as the black stuff on your bbq
    its just left over burnt stuff.


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