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Switch Vaccum to Gravity Petcock (83 Maxim 750)

Discussion in 'XJ Technical Chat' started by Samuel Veilleux, Jun 3, 2019.

  1. Samuel Veilleux

    Samuel Veilleux New Member

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    Hey guys, the title says it alot,
    I have a 1983 XJ750 Maxim with a bad Vaccum Petcock.
    The petcock let gas reach the oil pan when stored for a while.
    I live in canada and can't find a rebuild kit for the vaccum petcock so i ordered a gravity fed one.
    Bike will run as good?
     
  2. k-moe

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

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    Yes the bike will run as good, but the gas will still get into the oil.
    The thing that stops that from happening are the float needles in the carbs. You have one or more that are not sealing, or a stuck float.
    Pull the carbs for inspection, and plan on replacing the float needles and resetting the fuel heights.
    Have you ever gone thorugh the carbs since you've had the bike?
     
  3. Samuel Veilleux

    Samuel Veilleux New Member

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    Just did it, it's weird because it look like everything is new in the carb probably already been restored. Float Needle and where it sit look brand new, the black rubbery tip look great on every of them.
    One of the valve float was stuck on the little hook of one of the needle but i solve the problem by bending it a little bit by the outside.

    Only thing i haven't done is resetting the fuel heights, any tip to do it?
     
  4. Jetfixer

    Jetfixer Well-Known Member

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    The after market peacocks work fine except when you forget to shut fuel off :mad:, xj4ever has the rebuild kits for the stock petcock .
     
  5. Samuel Veilleux

    Samuel Veilleux New Member

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    Yea this is what i saw on a post
     
  6. XJ550H

    XJ550H Well-Known Member Premium Member

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    Setting the fuel levels


    [​IMG]
     
  7. Jetfixer

    Jetfixer Well-Known Member

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  8. XJ550H

    XJ550H Well-Known Member Premium Member

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    gets
    same with me when I try to text
     
  9. Jetfixer

    Jetfixer Well-Known Member

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    Guess I'm "old" ...
     
  10. XJ550H

    XJ550H Well-Known Member Premium Member

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    my phone folds im old too
     
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  11. Samuel Veilleux

    Samuel Veilleux New Member

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    Hey guys! I have a problem with my left turn signal. I put the turn signal on and its not blinking at all, it does turn on in the front( not in the back) but its not blinking. In the back i don't have any light, weird thing is that it was working all properly 30min ago. The light in the dash turn on too. Right side there is no problem except if i leave it on too long it would stop blinking.

    My bike is a Yamaha Xj750 Maxim
     
  12. raskal

    raskal Active Member

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    I'd suspect the rear light is burnt out
     
  13. k-moe

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

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    ^ or the socket needs to be cleaned ^
     
  14. Timbox

    Timbox Well-Known Member

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  15. Samuel Veilleux

    Samuel Veilleux New Member

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    Thx for the answers! Just realised that the rear light was burn, so not pulling enough Watts fo the blinker to go on!
     
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  16. Samuel Veilleux

    Samuel Veilleux New Member

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    Yamaha Maxim XJ750 1983

    Hey guys, my rebuild is getting together.
    But I have a small problem, the Bike refuse to Idle with the choke off.
    I don't think i have a Jet problem.
    It's weird because i can make the Bike Idle at 1k rpm with the choke open at like not even 5%.
    So basically I open the choke not even 1mm and the bike idle great and i can rev it to redline and it will go back to idle like it was new! I could basically drive the bike like that, but when i shut the 1mm of the choke it will go down to 600-700rpm and slowly die, if i give gas sometime it will go back, rev up, fall down to 1k and then 600 and die, other time i will try to rev and it would just die immediately.

    Is it bad choke adjustement? Bad Idle Ajustement?
    I really don't think it's the carb, because it was running great before i remove the head to do the head gasket
     
  17. k-moe

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

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    Start by bumping up the idle speed adjustment once the engine comes to operating temperature.

    Also make sure that you keep the enrichment on until the engine is fully warm.
    As the engine warms the idle speed will climb, just ease off the enrichment lever gradually to bring the engine speed back down so it's not idling at 2,500 RPM with the enrichment on.
     
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  18. Samuel Veilleux

    Samuel Veilleux New Member

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    Hey Guys, here is video, you will understand my problem.
    So basically i can Rev the bike and go back to idle with the choke mid on.
    But as soon as i clode the choke the bike can't idle.
    I can rev it with the choke off, past 2.5k rpm bike run great but as soon that it go back to idle it slowly die if i don't rev it again.

    here is the video

     
  19. Samuel Veilleux

    Samuel Veilleux New Member

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    It's weird because the carb were running great 1 week ago and the bike could idle.
    I didn't touch anything since i was waiting for some parts and now it do that
     
  20. k-moe

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

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    I hear a misfire.
    We need to start ruling out things that are not carb related before we go back to the carbs.

    Pull one spark plug at a time. Hook it up to the plug wire and lay it on the head so the plug is grounded. Start the bike and confirm if there is spark at the plug.
    Repeat until you have checked all four plugs.
    I need to emphasze tht you have to do this one plug at a time in order to prevent damage to the TCI.
     

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