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Rough engine at 5000 rpm

Discussion in 'XJ Technical Chat' started by coffeyrt, Mar 23, 2012.

  1. coffeyrt

    coffeyrt Member

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    Hey guys. I am new to this forum. I just picked up a 82 XJ650 maxim. I am decent with car repair and am looking to learn how to work on bikes. The engine runs slightly rough at 5000 rpms and goes away after 5500 rpms. There's extra vibration and maybe some grinding or something within those RPMs. Does anyone know what I should be looking at first?
     
  2. splazoid

    splazoid Member

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    Start withvalve clearances up top - a loose valve can certainly cause all kinds of problems, and the bike shouldn't be ridden if they're out of spec.

    Another very imporant starting point for a new XJ'er is to check the rear brake shoes - they can come unglued, and totally cause all kinds of damage to you, and the bike.

    Does it include sounds that indicate lean/rich running? Carbs after the valves.
     
  3. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    LOOSE valves aren't the potential issue; TIGHT valves are (they tighten with wear, not loosen.) That doesn't mean you should ignore your valves however.

    These motors have a "vibe range" right around that RPM. Some vibration is normal; but the naturally stronger vibes at that RPM can rattle other components that don't rattle at other RPMs; like exhaust heat shields, etc.

    That being said, the "normal" vibration can be greatly reduced by getting the motor in a proper state of tune. Which is, as pointed out above, a matter of valve clearances and proper carb service and adjustment.
     
  4. coffeyrt

    coffeyrt Member

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    Thanks for the advice splazoid and bigfitz. I'll make sure to check those out and get the experience working on them
     
  5. splazoid

    splazoid Member

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    Be really careful with the valve cover gasket. You might be able to save it, if you don't damage it, and it has not turned from rubber to non-flexible plastic.

    If you have out of spec valves, check that adjustment thread for instructions on changing out the shims.
    After valves, check the carbs according to The Church of Clean
     

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