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XJ650 - loss of power until 3000rpm +

Discussion in 'XJ Technical Chat' started by StephenT, Aug 12, 2009.

  1. StephenT

    StephenT New Member

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    My XJ650 starts first go, every time. I've just finished restoring the bike. New valves, rings, all good. Compressions are all within +/-5. Blip the throttle to 3000-4000rpm, the revs go up quckly, release the throttle and it immediately returns to idle 1000rpm. However, when riding the ride the bike it lacks power (as if on 2 carbs), then at 3000rpms, it takes off like a 'scalded cat'. Also when riding (under load), backing off to change gear, the revs only return to idle slowly. I have cleaned (ad nauseum) the carbs, the butterflies are all equal, the circular slides are smooth, they move up and return smoothly. The slide shafts are polished, new jets, new needles, new springs, new shaft seals, and checked all are correct sizes. What would cause, under load, for 2 of the circular slides to 'drag' and when the engine gets to 3000rpm they appear to suddenly lift, but slow to return to their "home" position. Thanks, Stephen.
     
    StephenT, Aug 12, 2009
    #1
  2. Daplumma

    Daplumma Member

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    Carbs...pilot circuit.Make sure you have no intake leaks.Which cylinders are missing? Could be an ignition/coil issue.
     
    Daplumma, Aug 12, 2009
    #2
  3. lowlifexj

    lowlifexj Member

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    Check for vacuum leaks with a propane torch around the intake boots and around the airbox to carb boots. The slides work off vacuum poor vacuum=poor slide movment.

    Check out this write up by Rick http://www.xjbikes.com/Forums/viewtopic ... +test.html

    Have you tried a carb sync? At least a bench sync test to conferm they're close.

    Well that should get you started
    Good Luck,
    James
     
    lowlifexj, Aug 13, 2009
    #3

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