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High Idle When hot

Discussion in 'XJ Technical Chat' started by mellicott, Nov 19, 2017.

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  1. mellicott

    mellicott New Member

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    Hello everyone,
    This is my first post, I just bought an 85 Maxim-X about a month ago. It's been great, with a few issues that were easily resolved. Now it is doing this high rev (about 3K RPM) thing where it's like the throttle is stuck. It's only doing it after it gets good and warm, about 5 miles or so. Once it gets hot, like 10 miles plus it starts doing it worse and higher RPM's. It starts to climb by itself, but if I let the clutch out a little when stopped it brings it back down. I can usually figure this kind of thing out, but so far no answer. Other than this it seems to run like a beaut.
     
  2. wgul

    wgul Active Member

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  3. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    1.Vacuum leak
    Or
    2. Adjust your idle speed knob
     
  4. rocs82650

    rocs82650 Well-Known Member

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    Or the fuel level in the bowls is too high.

    Gary H.
     
  5. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    I wouldn't jump to that right away......
     
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  6. Jetfixer

    Jetfixer Well-Known Member

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    ^^^+1 Vacuum leak. when hot and doing this spray some carb cleaner around carb boots if RPM picks up there is leak. What condition are boots in are they cracked? Have you had carbs off recently? are you running stock airbox or PODS?
     
  7. Robb

    Robb Member

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    I had this happen last spring. Idled fine, then after 15 or 20 minutes up to 3g's. It ended up I had removed the exhaust and when putting back on had forgotten to tighten the nuts on the #4 exhaust. Whacked the side of my head with my right palm, tightened it up and has been fine ever since.
     
  8. Retromoto

    Retromoto Member

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    If you spray carb cleaner around the boots, also shoot it around the throttle shaft. Butterfly seals on the shafts can sometimes crack and cause leaks.
     
  9. Simmy

    Simmy Well-Known Member

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    I have experienced this and cured it with the mixture screws and carb synch. Slipping clutch at a stop brought it back down, same as you describe.
     
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