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Back fire

Discussion in 'Motorcycle Tech Talk' started by 1OldSchool, Apr 18, 2012.

  1. 1OldSchool

    1OldSchool New Member

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    I am new to this site, and I don't really know anything about bikes, but since I now own a Harley, I want to learn how to fix it myself. I have an 84 Sportster that what sounds to me is doing small back fires while running. This is even at an idle. It has an electronic ignition. I know I don't really know anything about bikes, but I was thinking maybe the ignition needs adjusted or timing. Any in put?
    1OldSchool, Apr 18, 2012
    #1
  3. cowboy

    cowboy Moderator Staff Member

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    welcome ,Many things can cause this , what kind pipes are you running ? are they baffled ? how long has your bike sat up over the winter ? also do you have a service manual for your bike ? if not you should get one , it will be one of the best tools in your box , did you or has the carb been removed then put back on ?
    cowboy, Apr 18, 2012
    #2
  4. Lucifer

    Lucifer Well-Known Member

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    Welcome and congrats on the Ironhead.... Step 1....Get a Factory Service Manual....A few things can cause that...probably not the timing or ignition....check for intake leaks,make sure the carb is clean and put in a fresh set of plugs...
    You will learn how to maintain it yourself because no one at the Harley dealership will know how...keep on top of the maintenance and you'll have a good reliable ride...
    Lucifer, Apr 18, 2012
    #3
  5. 1OldSchool

    1OldSchool New Member

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    Cowboy, me and a friend did pull the carb and clean it up. It really wasn't that dirty. The bike sat up all winter and was not started at all. I don't remember it doing this last summer before I parked it. I did put a new set of plugs in the bake.

    Lucifer, Cowboy, I am going to see if I can get a factory service manual today. I will start with the suggestions that you have made so far. And Cowboy, if there is something I did wrong when taking the carb off, please let me know and I'll see if I can correct that. Thanks for the tips so far.
    1OldSchool, Apr 18, 2012
    #4
  6. hotroadking

    hotroadking Super Moderator Staff Member

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    Check the plug wires, if they are not installed correctly
    they could be arc'in to the heads, I"ve see it with bad wires
    when they get wet shorting out, and one set with just a tiny razor
    thin cut, bike would cut out back fire.

    Other had the chrome HD plug covers, the rubber boot
    wasn't seating correctly and the plug was firing through it
    to the bolt on the head outside.
    hotroadking, Apr 18, 2012
    #5
  7. FLHTbiker

    FLHTbiker Moderator Staff Member

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    If you pulled the carb apart did you put new seals in it and did you use a new gasket. Also if you pulled the carb apart did the diaphragm get pinched when putting it back together.
    FLHTbiker, Apr 18, 2012
    #6
  8. cowboy

    cowboy Moderator Staff Member

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    look on ebay & different bikes shop on line for you manual , I got one for my 94 at www.badasschrome.com just go throu there manuals section , as for the back fires , you can check the plug wires by close the garage start bike & have soneone turn the lights off you'll a spark jumping form them if there cut of broken , as for the carb flht said , leaks around the intake wd 40 or a hand held propain touch unlit with bike running go around the intake if ideal , goes up you have a leak , ask away & someone here will jump in & help ya out:D
    cowboy, Apr 18, 2012
    #7
  9. bguillory66

    bguillory66 Active Member

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    Just don't take a long time to check for that spark in a closed garage....don't want to read about u in tha obituaries:roflmao:
    bguillory66, Apr 18, 2012
    #8
  10. joshbob

    joshbob Well-Known Member

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    Hee-hee! Welcome to Bike Talk, 1OldSchool. I had a couple of ironheads back in the day. Mine were points & condensor ignition. You have EI so it should still be okay. I really can't add to any of the things already said but will say again get yourself a service manual and study it. If you can find the time, read it cover to cover . . . . and good luck!
    Last edited: Apr 26, 2012
    joshbob, Apr 26, 2012
    #9
  11. 1OldSchool

    1OldSchool New Member

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    Well, I've changed the plug wires, and finally received my service manual. First time they ordered the wrong manual. My bike still wants to back fire. This weekend I will be looking for air leaks, but any other suggestions would be appreciated. My bike also has electronic ignition, so points are out of the picture.
    1OldSchool, May 3, 2012
    #10
  12. 1OldSchool

    1OldSchool New Member

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    My bike seems to be back firing out the carb. I'm not quite sure but the clamps that hold the carb onto the rubber seem loose and don't want to tighten all the way. I think I'm going to see if I can get some clamps that are just a bit smaller so I know they are tight.
    1OldSchool, May 28, 2012
    #11
  13. cardboard

    cardboard Well-Known Member

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    Hope you don't have any water in anything making this happen......:rolleyes:
    cardboard, May 28, 2012
    #12

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