81 Maxim xj550 Idle problems

Discussion in 'Motorbike Technical Discussion' started by bullingball, Apr 30, 2007.

  1. bullingball

    bullingball Guest

    My bike has been setting for a year or so, and I have totally rebuilt
    the carbs (4 of them. When the engine is cold, it starts fine and
    runs fine for 10 minutes or so. Then it basically runs rich from
    there. I can't get it to idle, and it runs like it is on choke. I've
    checked to make sure the choke is NOT on at all.

    I first had one of the carbs over flowing, so I changed the floats and

    I have taken the carbs apart 10 times, and I have made sure all the
    jets are open. I've replaced the seals, floats, etc, but the strange
    thing is that it runs fine for the first 10 minutes.

    I'm kinda stumped right now, and any help would be grateful.

    Email me at too!
    bullingball, Apr 30, 2007
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  2. bullingball

    Albrecht Guest

    It sounds like the float valves are sticking. Also, check the float
    level setting. That information is on the bottom of the
    CARBURETOR parts diagram on www.bikebandit.com, but the resolution is
    so poor I cannot read it.

    Setting the float levels is confusing because you have to do it with
    the carburetors on the bench, upside down.

    Suppose the manual calls for the float level to be 14mm plus or minus
    1 mm. When you measure from the carburetor body to the bottom of the
    float (which is on top because the carbs are upside down) a 15mm
    measurement would be a lower fuel level in the bowl and a 13mm
    measurement would be a higher fuel level.
    Albrecht, Apr 30, 2007
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  3. bullingball

    kekrause Guest

    I had a 850 Yamaha with Hitachi carbs and had a similar situation as
    yours. I had those carbs off a hundred times till I called a guy north
    of here who works on bikes. He said he was a Yamaha mechanic for years
    and saw this situation often. If you have Hitachi carbs, chances are
    this will fix you right up.

    Pull the plugs and clean them all up. Take the bike out for a ride and
    when it starts to run like crap, stop and pull the plugs, one by one.
    See which one(s) are sooted up. Then, check these carburators for the
    enrichener plug, a little plug with a rod with a rubber pad on the
    bottom that covers a hole that allows raw fuel into the carburator at
    the intake to the engine. Chances are, the rod is hanging up just the
    slightest bit, allowing raw fuel to enter in, giving you the situation
    of running with the choke on. Clean up the rods with some steel wool
    and put a touch of grease onthem so they close all the way. Fixed my
    850 up just fine and it ran like a top after that. I still buy all my
    tires from that guy for giving me that advice. Good luck.
    kekrause, May 1, 2007
  4. bullingball

    Albrecht Guest

    If the starting enricheners leak, they won't affect the mixture very
    much unless the engine is at, or near, idle RPM.

    The starting enrichener system does have a little valve just as you
    describe. It controls an air passage that bypasses the throttle
    butterfly, and when the valve is open, it does suck gasoline straight
    out of the float bowl.

    But, it can only do this when vacuum downstream of the closed throttle
    butterfly is high. If you have to use, say, half throttle to ride at
    highway speed, vacuum drops off and the starting enrichener system
    cannot suck gasoline out of the float bowls.

    If I wanted to check for a leaky enrichener valve, I wouldn't pull the
    spark plugs to see which one was sooted up, I would just put my finger
    over the air intake hole to find the leak, or squirt so carb cleaner
    into the hole.

    It's about 1/4 inch in diameter, and it's in the air inlet bell on the
    same side of the carb as the enrichener valve.
    Albrecht, May 1, 2007
  5. bullingball

    Mark Olson Guest

    Not true- just last Saturday I proved the enrichener definitely ruins
    your mileage if left partially on (unintended of course), by getting
    30 mpg on my ZG1000, usually at highway speeds I get > 40.
    Mark Olson, May 1, 2007
  6. Indeed. I've done it on any number of vehicles - mind you, the rich
    running usually alerts one, but I did it just the other day on the
    Ducati - left it partially on, for miles and miles.

    No doubt B12 has an explanation, though.
    The Older Gentleman, May 1, 2007
  7. bullingball

    Mark Olson Guest

    Sorry, I wasn't intentionally trying to make it appear you were
    saying something you didn't mean.
    You may be right. I suppose I could try it on the EX250, presumably to
    maintain 70-75 mph I would have to use half throttle. Most likely my
    SV650 also has enough power in reserve that I am barely cracking the
    throttle as legal freeway speeds.

    I still think leaving the enrichener on would result in noticeably
    increased fuel usage on nearly all bikes running at legal speeds,
    so I am betting that the cases where it wouldn't matter are far
    less common than those where it would.
    Mark Olson, May 1, 2007
  8. It does.

    Years ago, a friend ran a Virago 750 which had some horrible mods to
    airbox and filters, and he used to run it on partial choke (as we call
    it) to compensate.

    I know, I know.

    It ran reasonably well, but it drank fuel like a dipsomaniac.
    The Older Gentleman, May 1, 2007
  9. bullingball

    kekrause Guest

    Well, it looks as tho we can at least agree that if the enricher
    leaks, it will increase fuel consumption. Will it foul plugs and cause
    the bike to run rough? I say YES. Will cleaning up this situation cure
    the problem the man has? I say YES, been there, done that. Like I said
    earlier, I chased my tail for a while till this guy, who was a
    certified Yamaha mechanic told me EXACTLY what my bike was doing, what
    kind of carbs I had, what to look for, how to fix it, all over the
    phone, sight unseen. And after all, isn't that what we are trying to
    do here?

    Glad I could help, and cause a little trouble. Gotta love the
    kekrause, May 3, 2007
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