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Thread: Take a guess (I know this is a car site)

  1. #1
    Senior Member RACING JUNKIE
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    Take a guess (I know this is a car site)

    Pulled out the XR400 to go riding in the woods after being stored for a long time w/ occasional starts... it is a 1997. It starts up, sounds ok @ idle, no head noise, good compression. Overall, this bike looks like a virgin prom date & has very low hours. Fresh 100 octane fuel, clean air-cleaner too.

    In less than in a minute, one of the two header pipes is very hot... in two minutes, it is glowing orange (both are hot) A little popping on downside of rev. Never had a problem with her before... it is air cooled & a 4 stroke which is hard to kill. I have never pulled one apart... it is forien to me. It has 4 valves. Anyone ever heard of this??? Stuck valve???
    "I would walk through hell on Sunday before I fear the enemy"

  2. #2
    Senior Member RACING JUNKIE
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    Sounds like a sticking or possible bent valve to me.

    I'd pull the valve cover(s) and do a looky loo, spray some penetrating oil on all the valve stems and spin it over.

    The rockers are adjustable, they probably need adjusting anyway, get a manual for it if you dont have one and do a PM on the valve train first.


    Goodluck, Cp
    ***IN GOD WE TRUST***

  3. #3
    Administrator RACING JUNKIE
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    Sounds like the floats may be sticking a bit in the carb.Thats where I'd start,sounds gummed up some to me
    There Is 1 Thing Better Than Cubic Inches,,,More Of Them

  4. #4
    Senior Member RACING JUNKIE
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    one side running lean

  5. #5
    Senior Member RACING JUNKIE fla1976's Avatar
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    Lean

    X2 on the lean condition.

  6. #6
    Senior Member RACING JUNKIE
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    valve train issue.

  7. #7
    Senior Member RACING JUNKIE BEAST477's Avatar
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    Yep scoot, sounds lean. I'd pull the carb or carbs and check the main jet if its been sitting over six months I'd put new main jets in it. Even if you can see through them they could be gummed up and make them smaller than what they should be causing a lean condition. Seen it many times on snowmobiles from just sitting for the summer. Jets are cheap. The other parts aren't.
    BEAST477






    Only a rich man can afford to use cheap parts.

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  8. #8
    Administrator RACING JUNKIE
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    Guys think about what you're saying here.If it was lean the pipe would be stone cold.

    The cylinder have an over abundance of fuel and its burning it in the pipe.

    Meaning its getting too much fuel :wink:

    Carb or carbs need to be cleaned,main jet,pilot jet,also the needle and seat valve.
    There Is 1 Thing Better Than Cubic Inches,,,More Of Them

  9. #9
    Senior Member DYNO OPERATOR
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    It sounds lean to me also. One thing you might check while you are working on it is, since it has been sitting, the rubber boot between the carb and head will dry rot causing a vacuum leak. Look at that too.

    TS1955

  10. #10
    Senior Member RACING JUNKIE
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    sounds lean to me also ... maybe a mouse made a nest up in the carb ? I've seen that before


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