Baffled!

Discussion in 'Engine, Fuel and Exhaust' started by odie1962, Oct 7, 2009.

  1. odie1962

    odie1962 New Member

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    I have a 2002 FXDL with the twin cam 88" and on the way to work the other day it started backfiring and sputtering badly. It cleared enough to get it home for some diagnostics. Found the rear plug was carbon fouled pretty badly. Got it cleaned up and re-installed. Bike now idles poorly and the back jug puts out a small amount of black smoke while the front one is clear. Swapped the plugs with each other and it still does the same thing, Only the back cylinder has problems. If this were a fuel problem wouldn't both cylinders be affected? I am going to change plugs and wires today to see if that helps, but I would like other ideas to look into. Baffled as to why only 1 cylinder is acting up.
     
  2. glider

    glider Veteran Member

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    After the plugs and wires, if that doesn't cure the problem, check into an intake leak in the FRONT cylinder causing that one to run lean. Obviously it's fuel injected so also consider a fuel problem or injector problem as well.
     
  3. smkinnan

    smkinnan Active Member

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    I imagine there are many possibilities but this is usually only fire or fuel related. If you are sure your are getting good fuel to the rear, then perhaps a coil is the problem. Sometimes coils are built with two sides, in that one side works the front cylinder and the other the rear. I am not familiar with your setup or bike but I have run into this before.
     
  4. odie1962

    odie1962 New Member

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    Thanks, I will check... The bike is not fuel injected, it has a stock CV carb on it. Hope it is something simple though.
     
  5. glider

    glider Veteran Member

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    Different story with carb. Do a compression test on both cylinders and possibly a leak down test too. You'll know if there is a mechanical problem with the rear cylinder. Possible it's the plug wire.
     
  6. odie1962

    odie1962 New Member

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    I'm hoping it's the plug wire or maybe the coil, I don't like the alternative,
     
  7. NEWHD74FAN

    NEWHD74FAN Experienced Member Retired Moderators

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    Are there any other circumstances regarding the start of the sputtering problem? You may have picked up some bad gas, may have an obstruction in the fuel lines or varnish/debris in the carb, sticky CV needle or float needle. Just a good idea to check, because most problems usually have a root cause simple in nature.

    Try draining the float bowl in a clear glass to check, I would also replace both plugs...and check that the vacumn line to fuel inlet valve is not cracked, may also want to check if valve is working, by applying suction and seeing fuel drain out steady.