Mechanic's crew: i've tried everything

Discussion in 'OT Driven' started by noxxs, Jul 18, 2006.

  1. noxxs

    noxxs New Member

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    I'm getting some really poor acceleration out of my bike. when it runs, it backfires when i quickly let of the throttle, if i pull the clutch in and let the rpm's drop without revving, the engine will die. when i get on the throttle, it stutters for a little while and then gets going with less than desirable results.

    here's what i tried: first i thought it just wasnt getting any fuel, but no, fuel is flowing just fine out of the petcock and the fuel pump. then i thought it could be a clogged pilot jet, nope, cleaned them all out and nothing, checked the pilot air jets too, and all clean, i cleaned the spark plugs too just for the hell of it. after that i went to the airbox, i cleaned the filter and cleaned out the airbox...again, no improvement.

    after that, i started wondering if the air/fuel screw somehow got readjusted, so i readjusted them all to 2.5 turns out, nothing again. now i started wondering about the ignition coils. i tested both primary coils, they were within the tolerable resistance as stated by the clymer manual. after which i test the seconday coils, both come back with a reading of double the resistance of the max allowable.

    my question is do coils go bad in pairs like this, and when they do, will they both give an almost identical resistance reading? and if its not the coils, does anyone have any other suggestions.

    sorry for so much reading.
     
  2. DenT

    DenT New Member

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    i doubt that they went bad (coils)
    try float height ... despite fuel flowing from the petcock if the float height is off it can lean/richen your mixture...

    Also check for air leaks (properly seated boots and leaking airlines...) that'll also mess up your stuff...

    in fact i got a non running bike for 350 bucks and traced it down to a vaccume line, works like a champ now.
     
  3. Subie Driver

    Subie Driver Eye see what you did there.

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    Sounds like a timing or ignition problem. What bike? If it's a 4 cylinder, then, yes, the coil could be bad, causing the misfire. My Subaru is a 4 cylinder car, but only has 2 coils, it's called a wasted spark system, where it fires the spark for 2 cylinders at the same time, one on the compression stroke, the other on the exhaust stroke. So if a coil goes bad, it takes 2 cylinders with it. When my coil went bad, only one of them went, but it caused a misfire on 2 cylinders, resulting in symptoms almost exactly like you have.
     
  4. noxxs

    noxxs New Member

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    did some more work on it and found out that the #1 cylinder was dead on it. i laid all of the spark plug caps on top of their respective spark plugs and disconnected them one at a time. when 2, 3, or 4 were pulled, the engine almost died. but when i removed #1, nothing happened. i know for sure that its getting spark, and the spark looks just like the other cyliders. i did a compression test after that, and i thought that the #1 cylinder might have had a blown through piston, but i had good compression on all 4. i'm in canada right now for a race. but when i get back, i'm gonna go over everything in the fuel system and see if i can find anything.
     
  5. cactusman

    cactusman ever prickly, always stickly.

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    Just change the spark plug and see what happens..

    Also, what did your plugs look like (before cleaning, and now since you cleaned them and ran it some..) does #1 look any different?
     
  6. noxxs

    noxxs New Member

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    4 of course
     
  7. Buck-O

    Buck-O Guest

    WHen was the last time the carbs where synced?

    And waht kind of bike?
     
  8. tripod

    tripod New Member

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    CV carbs? Are all your vacuum slides moving freely? And not have torn diaphragms?
     

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