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Power loss and vibration ???

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  • #1

    Power loss and vibration ???

    I have recently experienced an odd vibration and loss of power when I am cruzing at speeds around 55-60 mph. I notice the power loss as I try to accelerate. Now what is weird is that it comes and goes. I don't hear anything that could signal a problem. I don't know if it matters but I have just started to experience a "skip" in 1st gear when under power and just before the my speed control (the lil lady yelling "SLOW THE F*** DOWN!") kicks in. Anyway,could this be a trans. issue? Coils? Something behind the bars? Any suggestions are more than welcome. As for the transmission I am planning a tear down this winter and doing the 2nd gear fix.
    Just ME and my 82 XJ 1100. Mac 4>1-2 1/2" open baffle shotgun, no octy, K&N pod filters, LED tail/brake light & directionals, 750 FD mod, Ear Cannon air horn, modified bars and dash. "Motorcyclists are all bound together by a brotherhood tie through their love of the sport, and what difference does it make what machine he rides as long as he belongs to the clan." Walter Davidson, Dec. 1920 edition of Harley-Davidson Enthusiast Magazine http://s851.photobucket.com/albums/ab78/justme1100/
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  • #2
    Might be the pick-up coil wires if you think 2 cylinders are dropping out.
    2H7 (79) owned since '89
    3H3 owned since '06

    "If it ain't broke, modify it"

    ☮

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    • #3
      I would think that I would lose speed as well. If I hold the throttle it vibrates but doesn't bog down as I would expect. As I haven't experienced this before I will check the wires and coils.
      Just ME and my 82 XJ 1100. Mac 4>1-2 1/2" open baffle shotgun, no octy, K&N pod filters, LED tail/brake light & directionals, 750 FD mod, Ear Cannon air horn, modified bars and dash. "Motorcyclists are all bound together by a brotherhood tie through their love of the sport, and what difference does it make what machine he rides as long as he belongs to the clan." Walter Davidson, Dec. 1920 edition of Harley-Davidson Enthusiast Magazine http://s851.photobucket.com/albums/ab78/justme1100/

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      • #4
        Would weak spark cause this? I see a very small crack in one of the coils. I am going to have to pull the tank and replace the coils soon, with cold weather right around the corner it will be time to start the winter tear-down.
        Just ME and my 82 XJ 1100. Mac 4>1-2 1/2" open baffle shotgun, no octy, K&N pod filters, LED tail/brake light & directionals, 750 FD mod, Ear Cannon air horn, modified bars and dash. "Motorcyclists are all bound together by a brotherhood tie through their love of the sport, and what difference does it make what machine he rides as long as he belongs to the clan." Walter Davidson, Dec. 1920 edition of Harley-Davidson Enthusiast Magazine http://s851.photobucket.com/albums/ab78/justme1100/

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        • #5
          You can also try running the bike on the prime setting if you think the automatic valve in the octopus isn't opening enough. I have 3 standards and two of them act-up at certain speeds going down the highway. When I switch the left petcock to prime, they both (bikes) immediately start firing normally again. Of course you might be able to run it while it is acting up for as long as you can, hit the kill switch, and coast to the shoulder. If head pipe pairs 1&4 or 2&3 are significantly cooler that the other pair, it is a possible coil or pickup coil problem. I cant speak of a possible fuel delivery problem because I am not familiar with the specials... If you do the road test, take a wrench and a couple of spark plugs in case you foul some.
          If it turns out to be one cooler pipe, you could have a fuel mixture problem, a stuck fuel valve in the carb, bad plug, bad plug connector (they get worse when hot) or a bad wire. A bad plug wire would probably exhibit misfiring at any rpm.
          Skids (Sid Hansen)

          Down to one 1978 E. Stock air box with K&N filter, 81H pipes and carbs, 8500 feet elevation.

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          • #6
            Originally posted by skids View Post
            You can also try running the bike on the prime setting if you think the automatic valve in the octopus isn't opening enough. I have 3 standards and two of them act-up at certain speeds going down the highway. When I switch the left petcock to prime, they both (bikes) immediately start firing normally again. Of course you might be able to run it while it is acting up for as long as you can, hit the kill switch, and coast to the shoulder. If head pipe pairs 1&4 or 2&3 are significantly cooler that the other pair, it is a possible coil or pickup coil problem. I cant speak of a possible fuel delivery problem because I am not familiar with the specials... If you do the road test, take a wrench and a couple of spark plugs in case you foul some.
            If it turns out to be one cooler pipe, you could have a fuel mixture problem, a stuck fuel valve in the carb, bad plug, bad plug connector (they get worse when hot) or a bad wire. A bad plug wire would probably exhibit misfiring at any rpm.
            OK, (1) I have no octy so that isn't it and (B) I have checked the plugs and they are fine. I noticed last night as I was returning home from a ride that when I turn right the problem goes away. There were a few times yesterday the vibrations were really bad. So I am thinking short. Would this reduce coil output? Cyl. don't seem to be cutting out but I do notice reduced power. So will be checking the elec. system. P.S. I don't have a special but a Maxim (XJ) model.
            Just ME and my 82 XJ 1100. Mac 4>1-2 1/2" open baffle shotgun, no octy, K&N pod filters, LED tail/brake light & directionals, 750 FD mod, Ear Cannon air horn, modified bars and dash. "Motorcyclists are all bound together by a brotherhood tie through their love of the sport, and what difference does it make what machine he rides as long as he belongs to the clan." Walter Davidson, Dec. 1920 edition of Harley-Davidson Enthusiast Magazine http://s851.photobucket.com/albums/ab78/justme1100/

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            • #7
              Have you thought about the problem coming from the clutch? If it happens only on accelleration, you might think about it. I have a slipping clutch, and there are similarities to what you're talking about. Seems like it's losing power, but it's actually the clutch slipping under pressure. Chris

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