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Engine vibration above 4500 rpm

Discussion in 'XJ Technical Chat' started by Sed8d, Jul 2, 2016.

  1. Sed8d

    Sed8d New Member

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    Hello & Happy 4th!!

    Took the xj650 out for my first long ride today. Noticed a significant vibration when I hit 60 mph. Double checked & its related to engine speed, not cruising speed, so after 4500 rpm, it starts. Almost feels like a bearing....idk. No knocking and it runs fine under 60 mph. Any suggestions?
     
    Jetfixer likes this.
  2. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    If it's only happening above 60 MPH then it's not engine related.
    Does the vibration occur above 4500 RPM when in first gear?
    Are the wheels and tires balanced?
    Have you inspected the u-joint?
     
  3. Alan63

    Alan63 Active Member

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    Swing arm bushings?
     
  4. Sed8d

    Sed8d New Member

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    Sorry for the confusion. I noticed it in 5th gear at 60 mph., but I usually shift at 4500 rpm which is why i didn't notice it in other gears. It's def rpm related...I feel it in any gear above 4500 rpm. I'm sorry for not being clear.

    its a high frequency vibration, the same type of vibration you'd feel running over a washboard at high speed. It's an all or nothing issue too. I don't feel it or hear it below the 4500ish rpm, then bam.

    That's why I noticed it today as I was on a long road trip and cruising at higher rpm. Normally Ive been driving local, slow speeds, low rpm shifting. 1-5th gear up to 4500 is fine. Any gear over 4500 & the vibration kicks in. It's feels like the motor will literally vibrate itself apart.
     
  5. cgutz

    cgutz Well-Known Member

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    Are your valve clearances checked and in specification?
     
  6. Sed8d

    Sed8d New Member

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    Haven't checked the valve clearances, but that sure makes sense. I have a Haynes shop manual and a Yamaha manual on order. I understand engines, but don't have much experience with motorcycles. Is this something a newbie should attempt?
     
  7. Jetfixer

    Jetfixer Well-Known Member

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    I see your in Naperville? I live in Hobart In
     
  8. Jetfixer

    Jetfixer Well-Known Member

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    Adjusting valve shims is easy
     
  9. Sed8d

    Sed8d New Member

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    Very cool Jetfixer! You're practically just down the street. I work in Chicago Heights. I can prob see your house from work!

    Any special tool or parts I should get before attempting this? I hope it's the valves being out of adjustment. I don't know what else it could be.
     
  10. Yardawg

    Yardawg Active Member

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    I was very intimidated about checking my valves too. It really is very easy to do once you get started!
     
  11. Sed8d

    Sed8d New Member

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    Ok... I'll give it a try! Keep you posted.
     
  12. Jetfixer

    Jetfixer Well-Known Member

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    I can walk you though it if you would like the help.
     
  13. Jetfixer

    Jetfixer Well-Known Member

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    phone number removed by SnoSheriff
     
    Last edited by a moderator: Jul 17, 2016
  14. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    OK there is a normal increase in high-frequency vibration at 4500 RPM (actually peaking at 4500 rpm). Valve clearances being in spec are necessary, but not related to the vibration. Carbs being in synch will reduce it to a minimum, but it is the nature of the beast.
     
  15. waldreps

    waldreps Active Member

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    These motors have a natural harmonic vibration in that range. Mine happens at 5200 rpms. If it happens at your rpm and then stops above that, I'd think it's normal. Having everything in tune minimizes it but it probably can't be totally eliminated.
     
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  16. Jetfixer

    Jetfixer Well-Known Member

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    Harleys vibrate all the time. Lol unless it vibrates so bad your handle bars fall off probably not serious. Inspect all engine mounts for loose or cracked case is one thought.
     
  17. Stumplifter

    Stumplifter Well-Known Member

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    Right at 5k for mine. Although it feels far from like it wants to fall apart, just a buzzy, harmonic little purr type thingy that is noticeably different then through any other RPM.
    But, as others have mentioned, make sure your bike is tuned proper.

    Valve adjustment:
    http://xjbikes.com/forums/threads/airhead-valve-adjustment-with-pics.14827/
     
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  18. cgutz

    cgutz Well-Known Member

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  19. Sed8d

    Sed8d New Member

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    Thanks guys.

    Jetfixer I put your number in my contacts. Much appreciated.
     
  20. Jetfixer

    Jetfixer Well-Known Member

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