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  • Excessive carbon on the intake valves and pistons

    I'm the first post in this section!! Anyway, I started cleaning my pistons and heads up to get it ready to reassemble, and I couldn't believe how much carbon is on the pistons and on the intake valves. With only 12K on the heads and pistons, it's in pretty rough shape. Carbon on the intake valves is 1/8" think. Any ideas?
    Justin, HERD member 00016
    97 Fatboy

  • #2
    Have You already done a rebuild on this engine???
    I have tried the Chrome rings in the Shovelhead engines and have had no kind of success with them breaking in,did a teardown on the topend and replaced with iron rings and topend stayed dry after that.
    Ear Tag no. 00030

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    • #3
      Originally posted by autotec View Post
      I'm the first post in this section!! Anyway, I started cleaning my pistons and heads up to get it ready to reassemble, and I couldn't believe how much carbon is on the pistons and on the intake valves. With only 12K on the heads and pistons, it's in pretty rough shape. Carbon on the intake valves is 1/8" think. Any ideas?

      Check the valve guides for wear. Excessive wear will allow oil to pass through and carbon build up can occur.

      As well, who owned it before you? Cheap gasoline, low rpms, frequent idling and that crappy EPA N-Grind cam that's in there isn't doing anyone any good either.

      Make sure the spark plug heat range is correct.

      I'd start running a good detergent gasoline and maybe an additive as well in the fuel.
      Last edited by Dave63; 04-15-2010, 06:56 AM.
      **Note: The technical info I provide is suggestive. I am not a perfeshunel.

      "No two motorcycles should be the same. Your bike should be based on your creativity, and whatever's going on in your life at that time..." Jesse James


      HERD Member #10

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      • #4
        It was my brother-in-laws bike before I bought it. The S&S heads, S&S 561 grind cam and 10-1 pistons were installed 12K ago, maybe he just lugged it around everywhere. I know when I bought it, he warned me that I shouldn't take it above 4500 due to the big cam. (his words, not mine) I can't imagine the valve guides would be wiped out yet, maybe all he has is poor quality gas around him. Or maybe I'm just anal about all of my vehicles. I'll try to clean it off before I put it back together.

        Could it be the vent tube coming off of the heads that go into the carb/intake manifold? I noticed that they just had a couple of big o-rings wound around the bolts that go into the breather port in the head. It was not sealing well, you would think they would use a copper washer like they do in a brake caliper. The more I work on this bike, the more I find things that just aren't right. It drives me nuts.
        Justin, HERD member 00016
        97 Fatboy

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        • #5
          Originally posted by autotec View Post

          Could it be the vent tube coming off of the heads that go into the carb/intake manifold? I noticed that they just had a couple of big o-rings wound around the bolts that go into the breather port in the head. It was not sealing well, you would think they would use a copper washer like they do in a brake caliper. The more I work on this bike, the more I find things that just aren't right. It drives me nuts.
          The head vents vent oil vapor OUT of the top of the engine and into the intake system. How much actual oil it vents depends on the condition of the "umbrellas", your breather timing gear condition (because it's plastic) inside the cam chest, and the RPMs the engine is commonly run at.

          Could it be a contributing factor? Sure..... oil directly into the intake will burn to the backs of the valves, eventually.

          You could always buy a vent kit and just run the vents down below the bike, and vent it off into the atmosphere.

          Are the O-rings or poor seal the cause of your issue? No...

          Cold cylinders, poor gas, leaking valve guide seals, worn valve guides, worn rings and crappy fuel all contribute to carbon build-up.
          **Note: The technical info I provide is suggestive. I am not a perfeshunel.

          "No two motorcycles should be the same. Your bike should be based on your creativity, and whatever's going on in your life at that time..." Jesse James


          HERD Member #10

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          • #6
            I guess I'm going to blame it on crappy gas. I have the valves and pistons soaking in some carb cleaner now, that stuff usually melts the carbon right off of parts. Thanks for the info, you learn something new everyday on these things. LOL.
            Justin, HERD member 00016
            97 Fatboy

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            • #7
              Pistons and valves look brand new. Carb cleaner worked ok, but the Seafoam work awesome. Rings just showed up today, gaskets are sitting in the garage, maybe I can have it running by Sun.
              Justin, HERD member 00016
              97 Fatboy

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              • #8
                sounds like its burning oil..maybe guides are shot some people still beleive in knurling them, when rebuilding an engine and its just a waste of time.remember to check valve has to be open when checking
                09 Softail Springer FLSTFBT "AKA" Heritage Fatbones Touring
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                • #9
                  Not trying to hijack the thread, but I used to pour...slowly...tranny fluid in my carberator and keep it revved to keep it from dying. The tranny fluid creates steam in the combustion chamber and will clean up carbon deposits really well. It smokes a lot when it's being done, but the carbon will blast out of the exhaust and make combustion good again. I used to do it about once every year on my 283 chevy motor and the hopped up 350, both which I built myself.

                  Now, out of curiosity...does anyone know if this would work on my bike, an EFI '09? Say I take the air filter off and put some tranny fluid in a spray bottle and spray it in the intake while keeping it revved enough to not die. I know it shouldn't hurt, but since I've never tore apart or put together a motorcycle engine, especially anything with EFI or anything like that, I'm not real sure.
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                  • #10
                    Originally posted by yochanon View Post
                    Not trying to hijack the thread, but I used to pour...slowly...tranny fluid in my carberator and keep it revved to keep it from dying. The tranny fluid creates steam in the combustion chamber and will clean up carbon deposits really well. It smokes a lot when it's being done, but the carbon will blast out of the exhaust and make combustion good again. I used to do it about once every year on my 283 chevy motor and the hopped up 350, both which I built myself.

                    Now, out of curiosity...does anyone know if this would work on my bike, an EFI '09? Say I take the air filter off and put some tranny fluid in a spray bottle and spray it in the intake while keeping it revved enough to not die. I know it shouldn't hurt, but since I've never tore apart or put together a motorcycle engine, especially anything with EFI or anything like that, I'm not real sure.
                    You risk the chance of ruining 2 expensive O2 sensors. You'll also likely set a code, as the O2 sensors see trans fluid as fuel, and will set the ECU to full lean, to compensate for the artifically added fuel. I wouldn't recommend it. You can achieve the same result with water.........

                    The porpose of using trans fluid was because when mixed with your gasoline, it acted as a top-end lubricant for the valves and guides in older cars.

                    Any time you have an excess of carbon build-up on pistons and valves, it's due to a mechincal issue that's causing excess oil consumption, or a poorly set up machine, and/or a multitude of short trips. If it exceeds a certain level, physically removing it via rebuild is the remedy.

                    Fuel additives (detergents) can help prevent it, but fixing the source is the best remedy......
                    Last edited by Dave63; 08-10-2010, 11:07 AM.
                    **Note: The technical info I provide is suggestive. I am not a perfeshunel.

                    "No two motorcycles should be the same. Your bike should be based on your creativity, and whatever's going on in your life at that time..." Jesse James


                    HERD Member #10

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                    • #11
                      I never did track down the issue. I'm thinking it was a combination of a few things. 1. The oil coming from the breather that goes directly into the carb. 2. Poor gas 3. Carb jetting 4. Prior owner lugging the engine.
                      Justin, HERD member 00016
                      97 Fatboy

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                      • #12
                        Originally posted by Dave63 View Post
                        You risk the chance of ruining 2 expensive O2 sensors. You'll also likely set a code, as the O2 sensors see trans fluid as fuel, and will set the ECU to full lean, to compensate for the artifically added fuel. I wouldn't recommend it. You can achieve the same result with water.........

                        The porpose of using trans fluid was because when mixed with your gasoline, it acted as a top-end lubricant for the valves and guides in older cars.

                        Any time you have an excess of carbon build-up on pistons and valves, it's due to a mechincal issue that's causing excess oil consumption, or a poorly set up machine, and/or a multitude of short trips. If it exceeds a certain level, physically removing it via rebuild is the remedy.

                        Fuel additives (detergents) can help prevent it, but fixing the source is the best remedy......
                        Oops! Just remembered I posted this here! Thanks for the answer Dave...makes sense. I only did it that 'once a year' thing just for the hell of it. I always read the plugs and by how well or poorly the motor was running...seat of the pants stuff.

                        Anyway, again sorry for hijacking and appreciate the answer Dave...kept me from ruinin' stuff I can't afford, heh heh.
                        Spread the word! Learn about Jury Nullification! Help take back our country from
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