3 plugs - perfect tan color, 1 plug - dry fluffy carbon

Discussion in 'Mechanics Garage' started by flummerylove, Feb 27, 2012.

  1. GreyVF750F

    GreyVF750F Member

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    That plug is fuel fouled, not oil fouled. Squirrellyman has a point. Low/weak spark will not burn all the fuel properly and foul plug. Swapping the coils is a quick test. Possible bad plug wire. Swap that too. Check CDI box connections also.

    If all that checks out then it's back to the carb. Possible wrong pilot screw needle or damaged?? Is this happening at just idle or are you road testing?
     
  2. Dukiedook

    Dukiedook New Member

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    Swap coils/plugs to suss out possible electrical problem, could be just a fouled out plug like said above.
     
  3. Maggot

    Maggot New Member

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    With that plug being dry all the time you may not be getting any fuel to the cylinder. Pull the plug wire off that cylinder and run the bike for a minute. Then remove the plug and see if it is wet. If it is still dry, no gas!
     
  4. Maggot

    Maggot New Member

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    Check your spark while the wire is off by putting a plug in the wire and grounding it against the engine. Turn it over and look for spark.
     
  5. squirrelman

    squirrelman Member

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    A big, fat, blue spark, not a weak orangeish one.

    A healthy ignition coil should throw a spark about 7mm to ground.
     
  6. Dukiedook

    Dukiedook New Member

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    Spark gap checker works well in these situations.
     
  7. GreyVF750F

    GreyVF750F Member

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    Yea....telling your friend "here hold this a second"..................
     
  8. Maggot

    Maggot New Member

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    That's the best test.......nothing like a verbal conformation of spark strength!
     
  9. flummerylove

    flummerylove New Member

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    Ok swapping them coils now. Haha nice button
     
  10. flummerylove

    flummerylove New Member

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    The spark on the problem child cyl is throwing about 7mm to frame, but its lookin orangeish. Bright daylight however. The adjacent cyls spark appears to be the same, but that plug is yummy. Will swap coils now. Do coils fade out when they are spent? Ignition wires fade as well?
     
  11. flummerylove

    flummerylove New Member

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    Grey750f this is happening during road test and idle. Took the bike out for a all day flogger and the problem plug went from dry fluffy black to wet gassy black
     
  12. tinkerinWstuff

    tinkerinWstuff Administrator Staff Member

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    generally the plugs or the wires IMO. Swapping all three around and seeing where the problem follows will help narrow it down.

    You can probably get what you need for new wires from the local auto parts store. Bring in the old wires to a competent store and they should be able to make up a set to match as opposed to buying from Honda. I know I made a set for my '85 500 and just reused the screw on ends that attach to the coil and the grommet. Haven't paid much attention to what the 3rd gen uses for wires.
     
    Last edited: Mar 14, 2012
  13. GreyVF750F

    GreyVF750F Member

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    I doubt it's the coil. Because one coil fires to different cylinders. Your only having problems with one. So it's either the plug, plug wire or resistor in that plug wire end at the plug,which sounds like you have a good spark. It takes three entities for combustion. Fuel, which you are getting, spark ti ignite , which you have and compression. You mentioned new rings. Were the cylinders honed properly? All rings installed right? Does that cylinder have compression and how much?
     
  14. flummerylove

    flummerylove New Member

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    Swapped 2 coils & wires, problem no follow. Cylinders were honed by the best race shop in town bar none. Pistons were teflon coated and I installed new rings. I was super meticulous about this...however I very well could have screwed pooch on this cylinder. The gaps were in triangles from each other and could have moved upon install. Ring placement can effect compression completely..correct? Could it be the bike was beat to shit before I bought it and the cyls were worn past spec. All cyls would be showing symptoms instead of just one? The V4 is damn tough..this common?
     
  15. flummerylove

    flummerylove New Member

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    duh improper cyl test. will get at tomorrow.
     
  16. squirrelman

    squirrelman Member

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    It takes a bit of riding to get rings proppaly seated, but if your mechanic didn't check the ring END GAP, something coulda screwed up.

    When do you plan a compression test ?
     
    Last edited: Mar 14, 2012
  17. flummerylove

    flummerylove New Member

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    Thursday I will get a solid comp test done. Rings have about 9k on them. I rode her hard right out of the gate for the first 20 miles then changed immediately. Then a few changes around 2-500 mi. END GAP...now I recall not really giving that eagle eye for some reason. Prolly cuz I was fried from obsessing on crankcase for a week. If the gap is too small...compression issues.... doink :twitch:
     
  18. squirrelman

    squirrelman Member

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    B4 replacing rings you need to measure the cylinder diameter to see that's it's still within proppa specs.

    Also, you need to place each ring squarely into the cylinder about 1" down and measure the ring end gap with a feeler gauge.

    The most likely thing to go wrong if things are not correct is a ring with insufficient end gap expanding with heat, cracking, loosing compression and scoring the cylinder wall.
     
  19. flummerylove

    flummerylove New Member

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    Precisely what I needed to know squirrelman. That proceedure was not done. I reealy hope I am lucky. Doing comp test now.
     
  20. flummerylove

    flummerylove New Member

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    I now recall dude at racing shop measuring I.D. of cyls. He would have not proceeded if they were worn past 70.10mm, so good there.
     
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