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Carb issues XJ650 4KO

Discussion in 'XJ Technical Chat' started by Grant Murray, Jul 17, 2023.

  1. Grant Murray

    Grant Murray New Member

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    I recently rebuilt the engine of my 1981 XJ650 following it sitting for about 10 years. Although the rebuild went ok apart from the usual broken studs etc, I have been unable to get the bike to run properly. I have stripped, cleaned and checked the carbs 3 or 4 times now but I am still having the same problems of the bike backfiring and missfiring and generally not wanting to run properly. Has anyone had any similar issues
    and how did you cure them.
     
    Grant Murray, Jul 17, 2023
    #1
  2. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    1. Airbox it pods?
    2. OEM jets or aftermarket?
    3. Valve clearances done?
    4. Where did you get your rebuild parts?
    5. Wet set?running Synced?
    6. Fuel filter?
    7. Troubleshoot petcock?
    8. Troubleshoot TCI?
    9. Got your jets in the right locations?
    10. Got you coils and plugs hooked up right?
     
    hogfiddles, Jul 17, 2023
    #2
  3. Grant Murray

    Grant Murray New Member

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    Thanks

    I used all OEM parts. Only thing I haven't done from your list is the valve clearances so I will have a look at that and the set up again.
     
    Grant Murray, Jul 18, 2023
    #3
  4. chris123

    chris123 Active Member

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    Related to # 8 check the resistance on the coils. Weak spark could cause misfires, probably not backfired though.
     
    chris123, Jul 21, 2023
    #4
  5. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    Has a running (vacuum) synch been performed on the carbs?
     
    chacal, Jul 21, 2023
    #5

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