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Sudden loss of power.

Discussion in 'XJ Technical Chat' started by tomudei, Aug 2, 2006.

  1. tomudei

    tomudei New Member

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    Hey guys and gals!

    My '85 XJ750XN (Maxim X) is all of a sudden losing power mostly on hills. It doesn't matter what gear I am in, turn the throttle and it is very sluggish with no power. Doesn't do it all the time and seems to be intermittent.

    Any thoughts on where I might start or what might be most likely?

    Thanks for any help in advance.
     
  2. Robert

    Robert Active Member

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    Welcome to the forum Tomudei. I'm not an X'er myself but someone from that part of the family will be along shortly to help you out. Just a quick welcome aboard.
     
  3. HooNz

    HooNz Member

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    Ist guess would be fuel flow related stuff , and Hi too , so if you try to put the fuel tap on prime when it does it [assuming you have a prime] and it comes good then is the vacuum line or tap/filter , if no change you might have got bad fuel at the last refill?

    How long has it bin doin it?
     
  4. faighaigh

    faighaigh Member

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    Tomudei.

    I have the same fault with my bike, great downhill or on the flat but barely able to keep from stalling once she's pointed uphill. I think my problem is fuel starvation and the advice of the people on here has been to check out the petcock filters and carbs. The carbs are currently of the bike and I am in the process of cleaning them, again!

    Let us know if you get a solution.

    Faighaigh.
     
  5. tomudei

    tomudei New Member

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    Thanks for the welcome and the tips!!

    I recently rebuilt the petcock so I am hoping that is not it. Perhaps it is just bad fuel. Will keep looking into it and let you guys know!!

    Tomudei
     
  6. tomudei

    tomudei New Member

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    Well, I have been unable to reproduce the problem in a while so I am hoping that it was just some bad gas. Thanks for the suggestions guys.
     
  7. RickCoMatic

    RickCoMatic Well-Known Member

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    Since the bike is "Pulling hard" ... going up-hill -- Check the Petcock Vacuum hose running from the manifold to the petcock. If it's not real vacuum hose; the hose can collapse on itself and interrupt the vacuum over to the petcock. This usually happens when somebody buys a new battery and thinks the clear line will "Look" better than the black hose.

    Your Float Heights could be way out of whack, too.

    There's a long list of things it could be; really. But, if its fine ... and, runs great until you put an uphill load on it ... I'd make a bet it was fuel supply related some way. Or you are way out of sync. Peek at the linkage and look for a missing screw. Something's keeping that bike from a power boost uphill.

    Sure its a Yamaha??? Sounds more like the bikes a "Rolls-Kenardly"

    Rolls downhill fine.
    Kenardly get-uphill; all the time!

    Where do I get this stuff???
     
  8. Robert

    Robert Active Member

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    Laugh a minute with you Rick, A+ for originality!
     
  9. tomudei

    tomudei New Member

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    Thanks for the tips. Will definately look into your suggestions. Did I mention that I love this site!!
     
  10. commitment-skateboards

    commitment-skateboards New Member

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    :cry: I'm having this exact problem? A machanic buddy of mine told me to check my points? I'll let you know how that goes.

    BUT, I feel like it maybe more of a fuel problem as it also does this at high speeds and wants to die out as the R's drop back? :cry:
     
  11. RickCoMatic

    RickCoMatic Well-Known Member

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    The Points?
    There's no Points on these XJ-Bikes!

    The Bikes have Solid State Ignitions.
    (Some not so solid as others ... but, we're all trying).
     
  12. commitment-skateboards

    commitment-skateboards New Member

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    So what tells the coils to fire then? the pick ups???
     
  13. Robert

    Robert Active Member

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    You guessed it Commitment. The pickups send a switching signal to the TCI and it in turn switches the coils on and off. Ought to have a look at your TCI circuit board, they have a habit of suddenly sprouting bad solder joints, leading to intermittent operation and other annoying behaviors.
    I had a bike shut down on me once, the negative battery cable had broken off of the back of the engine (its deep and dark back there for you uninitiated folks reading this). I limped home on a coat hanger that I wired between a engine cover bolt and the negative battery terminal.
     
  14. commitment-skateboards

    commitment-skateboards New Member

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    I'm no machanic, I just turn left or right depending on what's needed and hope it works?

    How will I know the TCI is bad? Actuall cracking? discoloration? and can I fix it? or find a replacement new, or do I have to go through the trouble of finding a nice used one?
     
  15. martinfan30

    martinfan30 Member

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    You will have to disassemble the TCI(CDI) box. Inspect the printed circuit board for cracked solder joints.

    Then resolder(CAREFULLY AS TO NOT CONNECT TWO CIRCUITS THAT SHOULD NOT BE CONNECTED!)the offending joint .
     
  16. FABFABINC

    FABFABINC Member

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    well sorry for the spelling english is my 3rd language . Can anyone help I was riding at 140 kpd and the my speed reducedd and it seemed like a miss fire or like a clogged cataly converter on a car that slugish feeling cant bring it over 120 kph now . Now before this happened I drove for about 30 on the reserve and finally fuelled up and then maybe 20 mins into the drive thats when this happeneed can it be the filter please someone help
     
  17. crimsonlung

    crimsonlung New Member

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    Well, Im thinking start with the spark plugs, its the easiest thing you can do at this point and can tell alot about whats going on.

    Pullem out and checkem, cleanem off, and run it up a hill again. If you got your power back, it could be as simple as a bad mix. I had the same problem going up hills.

    I think it may also have to do with your carbs, Im going to be cleaning mine pretty soon.
     

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