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xj750j dies

Discussion in 'Test Zone' started by maxim xjj, Jun 8, 2022.

  1. maxim xjj

    maxim xjj New Member

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    Hello to every one & I know you can tell me what is wrong with my 1982 Yamaha XJ750J bike. When I am going slow & I hit a bump a the engine dies but will restart in a minor flooded condition then start to run full throttle & one more is when I let off the throttle to come to a stop it dies. I have to rev the engine to keep it from dying & will idle normal waiting for the light to change
     
  2. McTavish

    McTavish Active Member

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    sounds like.. I could be wrong.. the bump jolts one of the plastic floats up.. sticks to carb body, and doesn't close. flooding. remedy is to straighten float assembly.
     
  3. k-moe

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

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    Maybe.
    Keep in mind that setting up floats takes a bit more than bending things...you got to bend them exactly.

    @maxim xjj

    How long have you had the machine, and what do you know about its history (prior owners, maintainance, etc.)?
     
  4. McTavish

    McTavish Active Member

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    yes.. I blame the P.O. in two of my carbs, the assemblies were twisted, causing floats to stick.
    as in priming the empty bowls, then overflow. tapping the bowl stops flow.--that kind of sticking.
    it did take alot of trial and error to eyeball it.
     
  5. k-moe

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

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    When you get time this winter, go back in and make sure it's all set correctly. The fuel levels have to be pretty-much spot-on to ensure proper running at all engine speeds.

    Setting the fuel levels
     
  6. maxim xjj

    maxim xjj New Member

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    I have only owned the bike for about 2 weeks I found boots without clamps, some with cracks, and vacuum lines off I am not sure where all go I've changed the oil, final drive oil & have put clamps on & bike runs better but still dies starts back up anyway to unstick the floats without tear down p.s. put vacuum line on the petcock idles better
     
  7. maxim xjj

    maxim xjj New Member

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  8. maxim xjj

    maxim xjj New Member

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    Thank you I am so-so with 2-stroke carbs on small engines & my dirt bike but this bike with 4 carbs gives me the is a different adventure so I came to the best for help
     
  9. Franz

    Franz Well-Known Member

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    With a cold engine start the bike and spray engine start or carburettor cleaner around the intake boots. If the cracks are right through the engine will rev without you touching the throttle. If the boots are cracked you can repair some damage with RVT l believe but if you need to replace them be careful as the intake stub bolts can shear off. You will need to remove the carbs to set float heights. Get a Haynes manual, check valve clearances before carburettor work. If the carburettors need synchronised valve clearances must be in spec to get this right.
     
    Last edited: Jun 11, 2022
  10. Franz

    Franz Well-Known Member

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  11. McTavish

    McTavish Active Member

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    what is winter ?
     
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  12. k-moe

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

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    When it freezes. I know that it's not something you have often, but it does happen there.
    But you bring up a good point. In your case it'd be better to work on her during monsoon season.
     
  13. k-moe

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

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    OK.

    Start here and do a lot of reading.
    The Information Overload Hour

    It sounds like the PO didn't keep up on maintaince, which is common.
    Unfortunately you will need to remove the carbs to check the condition of the float levels, and to make sure that the carbs are clean, but hold off on that until we do some more diagnosis.

    I'd reccomend checking the valve clearance. It's really common that people don't ever bother to check clearances, let alone change shims when needed.
    Bigfitz's AIRHEAD VALVE ADJUSTMENT with Pics - parts I & II
    If the valve clearances aren't in spec then she'll never run right, no matter how much work you do to the carbs.
     
  14. McTavish

    McTavish Active Member

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    oh ... 3pm you mean .
     
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  15. Timbox

    Timbox Well-Known Member

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    McTavish, I remember living in area that I could ride all yr round. It is great but then when the bike has to go down for service, it sucks. Or does it? That just means you need another backup bike when one is down being serviced.
     
  16. maxim xjj

    maxim xjj New Member

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    hey guys thank you for the advice I order new boots and let you know how that works out but now another problem on the left grip is a what I say is the choked cable that was stuck, I think, I went down to carb & push the plunger into the carbs & now it wont idle, run right & those plungers dont move with the cable at all
     
  17. maxim xjj

    maxim xjj New Member

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    Thank you I will do that next question How do you adjust choke cables properly
     

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