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  1. #1

    Join Date
    May 2020

    Default Starting problem with 75 ironhead

    Hello all iam looking for some help on my 75 ironhead I just got done rebuilding it this is the first ironhead I’ve ever worked on I got the bike last year it’s been setting for 22 years I tore it down split the case replaced bearings,rings,seals ect rebuilt carb and cleaned tank when it’s cold it starts 1st or 2nd crank (xlch) but after running it 10/15 minutes it will not restart I’ve checked spark,points,timing,push rod adjustment all in spec after talking to previous owner found that he had the problem any suggestions would be greatly appreciated
    Last edited by Dlk75; 05-21-2020 at 8:22 PM. Reason: Forgot to say thanks

  2. #2
    Senior Member

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    Join Date
    Dec 2017


    What is the compression when cold? and, ...What is compression when it is hot and won't start?

    When you rebuilt it did that include rebuilding the heads?

    You said you check pushrod adjustment - was that when it was cold?

    Is the spark still good when hot?
    Just wonder if coil is breaking down when it gets hot - do you have another to swap out?
    what type of plug wires you got? what about sparkplug caps? and sparkplugs? any of them resistor type?

    What carb on there? All settings confirmed, especially float height? Does it need to be choked when cold?

    No vacuum lines or spigots not properly connected or plugged?

    Is the carb hot when the engine gets hot and won't start? Have you confirmed the intake is sealed tightly with no air leaks?

    Fuel flow to the carb has been confirmed when running, and, when it won't start?

    Does it die when it gets hot, or do you just run it for 10/15 minutes then shut it off, then try to restart it?

    What about the condensor in the ignition system - did you change that? If you watch the points when it is running is there excessive arcing across the points?
    If so, that along with hard staring could indicate a faulty condensor.

    what about battery and voltage - fully charged and still supplying proper voltage when it won't start? Grounds all clean and tight?

    Have you actually ridden it, for more than 10/15 minutes?

    Does it make any different noises when it gets hot?
    Last edited by TriNortchopz; 05-22-2020 at 12:05 AM. Reason: batt

  3. #3

    Join Date
    Dec 2018


    Good troubleshooting list, T.

    "When you rebuilt it did that include rebuilding the heads?"

    Motors with worn out top ends and leaky valves can be hard to start, kicking, when hot. The fat mixture necessary for a cold start will mask an abundance of problems.


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