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Issues with 4 in 1 exhaust and acceleration

Discussion in 'XJ Technical Chat' started by Michael1981, Jul 15, 2021.

  1. Michael1981

    Michael1981 New Member

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    Hello together,

    my name is Michael, and i am from Germany.

    I am driving a XJ 650 4k0 with some issues with the exhaust.

    I bought the bike at the beginning of 2021. It was in a very bad condition. 20 Years in a barn looked not so good on it.

    The man had never problems with the 4 in 1 and the acceleration before. I rebuilded the carburator complete from crap to new.
    But when i drive around 5.000 RPM the bike stalls or jerks, hard to explain. It is like it would get too much or less from something.

    I searched through the Internet and in my Workshop. Than i realised, that my 4k0 had the Y-15 installed against the original Y-11.
    But my rebuild kit included only Y-11.

    Am i right, that the Y-15 decrease my symptoms with the 4 in 1?
    Now i am searching for an urgent solution till i can get a Y-15.

    Any ideas from the forum if there would be a Interim solution? I urgently need the bike on saturday morning.
     
  2. Polock

    Polock Well-Known Member

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    check your air filter first.
    a750 takes a Y-10 , a 650 a Y-11, i don't know where a Y-15 came from but maybe put the Y-11 in and see what it does
    most of the time a 4-1 doesn't need the needles changed, sometimes 1 size on the main jet
     
  3. XJ550H

    XJ550H Well-Known Member Premium Member

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    Did you remove the air Jets and possibly put them back in the wrong position?
    Is it possible one or more of your main Jets is not in the correct location switched with the pilot Jets?
    Did you check the diaphragms for holes?
     
    Mechanic1978 likes this.
  4. Michael1981

    Michael1981 New Member

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    My aftermarket rebuild kit had i guess Y-10. I have to check them again. Main Jet was switched from 100 to 102.
    I have no problems with the start and after 6.000 RPM. The XJ accelerates fine on both RPMs. Only between 5.000 and 6.000 the bike makes problems.
    But i can not figure out if it is to lean or too rich in this section. The airfilter is new. I took it off to test without it. But no improvement.
    I bought a replacement carburator which will arrive today. I will test the bike with it if it helps.

    The Y-15 are built in the 11R Version of the XJ 650. It is the throttled version.
    I dont know if the one who drove the bike before me built them in for the 4 in 1.

    My bike is the version with 71 hp, no throttled version. Never been.
     
  5. Michael1981

    Michael1981 New Member

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    Yes, i removed the air jets. Maybe i put 1 of 4 back in a wrong position. I will check this after work. But the bike dont smokes black from the exhaust, like i read often.
    Maybe with 1 wrong it wont. Idk.

    Main Jets and Pilot Jets are correct, for sure. The diaphragmas are all 4 in good condition. I checked them multiple times against bright light.
     
  6. XJ550H

    XJ550H Well-Known Member Premium Member

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    Annual at the picture of the air Jets the Jets are positioned correctly but they are mislabeled when I turn on my computer I will upload a picture of the proper location and proper labeling of the air Jets
     
  7. Mechanic1978

    Mechanic1978 Active Member

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    I just seen your withing a few miles distance of me.
     
  8. XJ550H

    XJ550H Well-Known Member Premium Member

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    The great Northwoods extends across the top of the United States I live in New Hampshire just shy of the Canadian border
     
  9. Mechanic1978

    Mechanic1978 Active Member

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    ohh wow... when I click on your location link it takes me to a google maps location of "north woods" apartments here in Indiana.. thats funny, guess your not then lol...
     
  10. Mechanic1978

    Mechanic1978 Active Member

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    sounds like your carbs have issues, maybe wrong jets in wrong holes, low float levels etc...even the worst hacked up exhaust will not effect the starting ability, and I have seen everything from no air filter to the ones you cant even see they were so dirty, and it still started. so the exhaust, and air filter have nothing to do with your cutting out. The 4-1 exhaust will only increase the valve backpressure a slight amount slowing the intake velocities a little... but will not effect the starting/stalling.

    It's your carbs!...
     
  11. XJ550H

    XJ550H Well-Known Member Premium Member

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    My favorite one when I click on my location is the great Northwoods septic design
     
  12. Mechanic1978

    Mechanic1978 Active Member

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    heres what coms up when I click it. I think google maps is using our current locations to search the area for the "north woods"
    woods.JPG woods.JPG
     
  13. XJ550H

    XJ550H Well-Known Member Premium Member

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    back to the issues
    correct photo for air jets
    jets.jpg
     
  14. Michael1981

    Michael1981 New Member

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    Hello all together, i want to give you a short update on my XJ.

    It runs!!! It runs without problems. I got a replacement carburator on friday and replaced the needles and the jets.

    Now it runs and also i could drive on the racing track "Hockenheim Ring" on saturday. Great experience.

    Thanks to you all for your help.
     

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