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Carberator problem?

Discussion in 'XJ Technical Chat' started by Littledragon, Aug 29, 2013.

  1. Littledragon

    Littledragon New Member

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    I have a 1982 XJ650 Maxim. When the motor gets hot the throttle does not close down properly when shutting off the gas to shift. When I pull in the clutch and close the throttle to shift the engine rpms don't fall off like they should. The rpms fall very slowly like the engine is still receiving almost the same amount of gas as if I had not closed the throttle for the shift. If I keep the clutch in the rpm gradually begins to fall after a few seconds. This only occurs after the engine is hot. I have had people tell me the carbs are out of sync but it seems to me the problem would be there all the time and not only when the engine is at normal operating temp.

    Any ideas about this would be appreciated before I take it to a shop and let go of my hard earned money. Thanks!
     
  2. RickCoMatic

    RickCoMatic Well-Known Member

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    Search: Clunk Test

    Or use link in my sig.
     
  3. bmarzka

    bmarzka Active Member

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    Take it to a SHOP??? NO, NO, NO!!! Honestly, everything you need to know about XJ's is right here. There's no need to take it to a shop. And you'll be hard pressed to find someone that will fix it right.
    Rickcomatic and BigFitz52 are XJ gods. They know EVERYTHING. Listen to them, my friend, and ye shall gain untold wisdom.
     
  4. Rayjay1959

    Rayjay1959 Member

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    Mine does the same exact thing. I do have the k&n filters. If you do too, that might be why. My bike was like that when I bought it.
     
  5. quebecois59

    quebecois59 Well-Known Member

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    Littledragon

    I seem to remember that bigfitz already wrote that a bike acting up when hot is a symptom of valves being to tight (not enough clearance).

    Have you ever checked your clearances? That would be a good start.
     
  6. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    Thx, QB--

    BigFitz is wearing out his keyboard dispensing the same advice that is on PAGE 1 of the MAINTENANCE section in the service manuals. (It's just not what they want to hear.)

    Thing is, doing it right works. I LOVE my 550, it's the most stone-reliable bike I've ever had. Plus it flat rips.

    To the OP:

    For starters, if you think a 30+ year old motorcycle is something you take to a shop every time something goes "burp" then you had better be made of money.

    Secondly, and just as important, a whole lot of shops either won't touch these bikes or will just take your money and make it worse.

    An old bike is a DIY proposition, it's not an '82 Chevy. Even DIY, you're looking at about $600 in parts when all is said and done (if you want to actually use the bike.)

    What you are (both) describing is called a "hanging idle." It is a symptom of the motor and carbs being OUT OF SYNC.

    To fix it you must:

    Properly clean, service and adjust the carbs; which includes wet-setting the float levels.

    GET YOUR VALVE CLEARANCES IN SPEC. A prerequisite to what comes next.

    After a good accurate bench sync, you reinstall the carbs and do a running vacuum sync, with YICS blocked.

    DO THESE THINGS, IN ORDER, and I guarantee you the bike will run the way you hoped.

    Ignore the advice, and continue to screw with it hoping for quick solutions, and you're gonna be at this for a while.

    I'd rather RIDE. (And I DO, with great regularity.)
     
  7. jmilliken

    jmilliken Well-Known Member

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    you guys both have classic symptoms of diaphram pistons not moving like they should..... you are both due for carb cleaning.
     

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