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Rear cylinder not cooperating

Discussion in 'Help Wanted' started by Atti2ude, Apr 7, 2013.

  1. bearman

    bearman Active Member

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    did you check your pushrod adjustment?
    another thing that would tell you if its something mechanical is comparing how fast each cylinder reaches the 250psi when checking the comression.
     
  2. Atti2ude

    Atti2ude Member

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    There wasn't a change in valve train noise so figured the pushrods were in adjustment. Each cyl took about 5 revs to hit 250 which is good but is that a conclusive test?
     
  3. bearman

    bearman Active Member

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    It is very conclusive. If the rear took two additional revolutions to reach the same pressure then that would mean that the rear cylinder isn't as mechanically heathy as the front, like maybe a stuck or broke ring or dirt on one of the valves or maybe a pushrod out of adjustment and not holding the valve open long enough. But the fact that they operate nearly identical means that your problem is most likely NOT mechanical.

    Another thing that I can think of for your problem is one of the wires or connectors from the ignition to the coil might be bad. See if you can test the continuity/resistance from back of the igntion connector to the coil on all three wires (with the wires still connected) and see if there is any difference, they should all three be the same. Be sure to wiggle the wires and connectors around to imitate engine vibration.
     
  4. Atti2ude

    Atti2ude Member

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    Found a bent pushrod

    Perfect riding weather and bike is still down. No local knowledge where I'm at so been doing a lot of reading on the forum trying to figure out the hell's going on. Removed the pushrod tubes and found the rear cyl exhaust pushrod is slightly bent. I'm sure this is contributing to the problem but what would cause this?

    I did a few more videos so you can see how the rear exhaust valve train is clearly troubled. In both videos you will notice that the movement is sluggish in comparison to the others, especially when the valve is closing. Before I start pulling things apart, it would be nice to know whether to target the rocker box or lifter. Any suggestions??

    Rear cyl exhaust valve; rocker box view - YouTube
    Rear cyl exhaust valve; push rod view - YouTube
     
  5. MN K9

    MN K9 Well-Known Member

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    Maybe you have a valve sticking.
     
  6. JeffM

    JeffM Active Member

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    Todd, i know we spoke while out fishing today, but after see the You tube vid's i did not see your pushrods turn.

    My old 80 cu evo had Edelebrok heads, S&S adjustable, roller rockers and black diamond oversize valves and if i remember rightly when i pulled out the plugs and hit the start button the pushrods turned slowly, to me your pushrods look too tight.
    Someone else chime in if you think i may have imagined it.
    I adjusted my push rods up till they touched then up 1 -2 turns and lock them off.
    Never had an issue with 105 hp in an EVO.
    As we said today maybe 2 new lifters and rods, cheaper than a head job.
     
  7. H3is3m2n

    H3is3m2n Member

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    I just had a similar issue, tested the blue lead for the rear cylinder and it was chafed inside the frame, replaced that section of wire and the bike is running great now.
     
  8. Slick-Dog

    Slick-Dog Active Member

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    Thats wild a buddy of mine has a 05 chop and it always sound it like it had a flat spot in it... but when reved up it went away...hummm I`LL HAVE HIM CHECK THEM OUT!
     
  9. Dusty.B

    Dusty.B Member
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    I know this is an old thread but does any one know what ended up causing @Atti2ude rear cylinder issue? I’ve been dealing with the same issue on my ridgeback project
     
  10. Vicki

    Vicki Member

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    Having the same problem as well.
     
  11. chubs

    chubs Guru

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    I'm sure that I'm probably wrong, but, thinking back it was happening on my bike, ( rear cylinder misfiring ) Took a while for a dummy like myself to find that the plug wire was loose at the coil end. plugged it in good and tight and no more problems for last few years. Just sayin.
     
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  12. bdm7250

    bdm7250 Guru
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    It's easy to overlook the obvious.
     
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  13. chubs

    chubs Guru

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    Ain’t that the truth!! When we have a problem with our bike, it’s. Always “. Oh no ! This is gonna be major expensive “ and we usually find that the last thing we’d think about is the problem!
     
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