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Engine vibration

Discussion in 'Help Wanted' started by HellOnWheels, Feb 13, 2017.

  1. HellOnWheels

    HellOnWheels Member

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    Recently changed stator on my 1999 Vintage Sport. Currently getting a high-RPM engine vibration. Engine is smooth through all gears until the upper end of the RPM range. In 5th gear, it occurs around 85mph and can be felt in the footboards.

    What's the most likely cause of this?
     
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  2. FrankBDPS

    FrankBDPS Well-Known Member
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    If it did not do it before the work was done it may be that something was left loose or not properly installed. Also check you're rubber mounts on the front of the engine and back of the transmission. Don't forget to look at the top mounts also. Let us know what you find. Good luck.
     
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  3. HellOnWheels

    HellOnWheels Member

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    A friend who is a reputable professional bike mechanic walked me through the disassembly and reassembly, so I'm pretty sure it's not an issue of something not being done "correctly". When I had the bike on the rack, I noticed that the front motor mount was all kinds of loose (like "the nut was all the way to the end of the bolt" loose) and I cranked it down. It got a lot smoother after that, but at low speeds.

    I was headed to a CoC meeting about 50mi away, almost all of it was non-stop high-speed highway travel and started noticing that right around 85mph, it felt like the bike was going to rattle apart. Throttling down to 84mph, it vanished.
     
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  4. FrankBDPS

    FrankBDPS Well-Known Member
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    You think you may have a tire issue maybe out of balance?
     
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  5. bigkelk9

    bigkelk9 Well-Known Member
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    Big dogs pre 2005 were no where's near as stable as post 2005, they made a lot of changes and you can tell the difference big time. But as far as what u are describing, sounds like what Frank said, a balance issue..
     
  6. HMAN

    HMAN Well-Known Member
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    fk it
    Peel the sticky stock wheel weights off and pour some Dyna-Beads in the tires. Smooth as glass, even @ higher end hiway speeds.
     
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  7. Dragonslave

    Dragonslave Active Member

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    :agree:
     
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  8. pauldeepsea

    pauldeepsea Well-Known Member

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    Did you check all of your motor mount bolts?
    Could be an alignment issue with the motor, primary, transmission?
     
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  9. cdogg556

    cdogg556 Guru

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    :agree:
     
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  10. HellOnWheels

    HellOnWheels Member

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    It's not a tire vibration issue, it's a motor vibration issue. I don't have a tach so I'm not sure exactly what RPM it's doing it, but it's at a certain point in every gear. The 85mph just happens to be where it does it in 5th gear.
     
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  11. woodbutcher

    woodbutcher Mr. Old Fart member #145
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    ??? fuel tank vibration ???
     
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  12. TapioK

    TapioK Well-Known Member

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    You mentioned the front motor mount was kind of loose, check the rubber on it, maybe it is cracked. Just replaced the front mount on a Harley, it vibrated like crazy. Cheap owner bought a new cheap part with hard rubber, engine still vibrated ... Got OEM part, smooth....
     
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  13. cdogg556

    cdogg556 Guru

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    On my 05 Bulldog I had something that seems real similar to what you are experiencing with your bike, somewhere in the 2500 to 2800 rpm range I would get a weird vibration that I could never figure out, took it to the local Big Dog Dealer at the time when they were still in business and they couldn't figure it out either, it wasn't so bad that I needed to deal with it right away, but it was irritating for sure, anyway I think about it now and was thinking maybe the clutch hub nut was coming loose or sumth'n like that and was causing the vibration, hope you figure it out, keep us posted.
     
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  14. Marky-Marc

    Marky-Marc Well-Known Member

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    Just my .02....sounds like an engine to frame alignment.....just what @TapioK said...check the other bolts and replace the RUBBERS...you tightening that one bolt or the others out of sequence....(shit happens) may have moved the engine to frame alignment.....
     
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  15. JMont

    JMont Member

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    I have motor bolted straight to frame on my 03 Mastiff. It vibrates like crazy at mid rpms. Just curious has anyone ever added rubber mounts or know if it should have rubber mounts??
     
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  16. TapioK

    TapioK Well-Known Member

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    Is yout engine top mount bolts tight? Common reason for vibrarion.. check all engine bolts while you are there...


    Sent from my iPhone using Tapatalk Pro
     
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  17. FrankBDPS

    FrankBDPS Well-Known Member
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    I think all the Mastif model bikes should be rubber mounted. It was actually a selling point back in the day. They were basically FXR style bikes with isolated motor and transmission mounts.
     
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  18. JMont

    JMont Member

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    Yea they all seem pretty tight. I think it's probably typical for my yr model, i just have never rode another one like it to compare to
     
  19. TapioK

    TapioK Well-Known Member

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    "Seem pretty tight" is not good enough. -03 has 107 engine, that doesn't vibrate too much. Less than 117.


    Sent from my iPhone using Tapatalk Pro
     
  20. JMont

    JMont Member

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    Hmm well I couldn't get a turn on them so they snug as i can comfortably tighten them. What else could possibly cause vibrations. And i can pull clutch in and it goes away so i kno its engine
     

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