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Thread: misfiring

  1. #1
    Join Date
    Jul 2010
    Location
    Vermont
    Posts
    867

    Default misfiring

    I’ll apologize in advance for a lengthy post, but I don’t know how to describe this otherwise!

    So far this season I’ve ridden my ’46 Chief over 3000 miles without too much fuss. At about 1000 miles I had some running problems so I took a week off and 1) removed and cleaned the carb, set the float again. 2) replaced the battery, 3) replaced the plug wires and plugs, 4) re-set timing, 5) checked the valve lash, 6) installed all new coil, condenser, points, cap and rotor…

    So I had 2000+ miles of good riding until Monday, the Chief stopped suddenly at a stop sign and wouldn’t restart. I found the ground wire had broken off at the battery terminal and I was able to do a roadside fix and continue. 30 miles from home main tank ran dry and I switched to reserve. A few miles later the engine misfired once or twice but I kept going. More miles and more misfires…. but between the misfires it ran normally for a few miles each time. Finally I was only getting a quarter mile or so of good running before the misfiring stretches.

    So, my first thought was bad gas in the reserve tank? Yesterday I rode the five miles to the gas pumps, it misfired a few times doing that. I filled it up and rode the five miles back home and it misfired several times doing that.

    Plugs look good I think:



    The cap had some arcing on the front post and a small groove on the rear post, there was brass dust in the distributor body. The rotor was okay and it cleaned up with a few brushes of steel wool.




    So I don’t know, it’s supposed to rain today so I won’t be riding but I also don’t trust it right now to get me home!

    How long would it take to run through some bad gas?
    Last edited by pisten-bully; 07-08-2020 at 11:20 AM.
    Pisten Bulley is Harry Roberts in Vermont.

  2. #2
    Join Date
    Sep 2005
    Location
    Sarasota, Florida
    Posts
    4,338

    Default

    I did have a problem with bad gasoline in my Chief a number of years ago, and the symptoms sound just like your's, Harry. Fresh gas, and purging all the bad gas fixed that problem. I also had similar symptoms with a poor ground wire. You may chase your tail for awhile before you find the true cause.
    Eric Smith
    AMCA #886

  3. #3

    Default

    Harry,

    I would check the charging system. When the ground wire on my Chief broke it smoked the ceramic resistor on the regulator and would not charge correctly.

    Dave

  4. #4
    Join Date
    Jun 2007
    Location
    Catonsville,Md.
    Posts
    194

    Default

    Recheck every connection you touched also!

  5. #5
    Join Date
    Jul 2010
    Location
    Vermont
    Posts
    867

    Default

    Quote Originally Posted by indian301 View Post
    I would check the charging system.
    Thanks Dave, that's interesting to think about! I pack along a small voltmeter and when it quit I found something like .7 volts when I grounded the meter to the motor and the other probe to the positive terminal of the battery, and when I next tested on both battery terminals I got 12.5+ volts and that led me to the ground wire. Indian Frank set me up with an electronic regulator about 10 years ago and it's been bullet proof and trouble free. I also have an auto reset breaker in line off the positive post of the battery, and the thought crossed my mind that the circuit breaker may be failing. And like Tomfiii suggests I'll check it all over before I venture too far away!

    It just seemed like the bad gas theory is logical because my misfiring didn't start until I switched to reserve, and I rarely go much more than 10 or 15 miles on reserve before stopping for gas...so some of that gas has been in there all summer! Too easy?
    Pisten Bulley is Harry Roberts in Vermont.

  6. #6
    Join Date
    Jul 2010
    Location
    Vermont
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    Oh, and thanks Eric, I’m hoping it’s as easy as bad gas! (...that is not a joke about Taco Bell!)
    Pisten Bulley is Harry Roberts in Vermont.

  7. #7
    Join Date
    Sep 2005
    Location
    Sarasota, Florida
    Posts
    4,338

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    As much as you ride your Chief, I know you will find the problem soon, Harry. It's the bikes that don't get out much that are so difficult to diagnose.
    Eric Smith
    AMCA #886

  8. #8
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    Jul 2010
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    Vermont
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    I’ve got no answer! Could’ve been gas, or it could’ve been distributor cap and rotor, those are the only two areas I addressed. All I know is today I had time for 40 miles and it ran great, zero misfires. About 20 miles on the main tank, 20 miles on reserve....but I had new gas in both tanks. And I cleaned the distributor cap posts and rotor....that’s all I did. So bad gas or bad ignition in the distributor.

    Tomorrow I’ll put 200 miles +/- on, I trust the Chief again!
    Pisten Bulley is Harry Roberts in Vermont.

  9. #9
    Join Date
    Sep 2012
    Location
    Saltsburg PA
    Posts
    377

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    How'd the trusty Chief do yesterday Harry? And by the way, what did you ever determine the cause was for the broken rotor a while back? Defective part?
    Jason Z
    AMCA #21594
    Near Pittsburgh PA (Farm Country)
    Allegheny Mountain Chapter http://amcaamc.com/

  10. #10
    Join Date
    Jul 2010
    Location
    Vermont
    Posts
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    Bah! I got 90 miles away and it started missing again. At first just an occasional misfire, but the frequency slowly increased to the point where it was time to call it quits, 30 miles from home. It couldn’t even sustain an idle without misfiring! I stopped once and changed out the cap and rotor, that effort gave me another 10 minutes (tops) without a misfire.

    Funny thing, in Vermont there are many locations without cell service, so I was at a general store using their phone to call my wife for a rescue. She didn’t recognize the number showing up on her phone because it was the general store’s number, and she had received an annoying robo call earlier...so she blocked my calls! All’s well that ends well, but I spent 3 hours trying to reach her...at least I was next to a river in the shade!

    The hunt continues! Jason, I think the rotors were somehow made wrong because I’ve been using older rotors and none of them have broken!
    Pisten Bulley is Harry Roberts in Vermont.

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