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Commando Quits

Discussion in 'Norton Commando Motorcycles (Classic)' started by M2TOY, Aug 12, 2019.

  1. M2TOY

    M2TOY

    Joined:
    Aug 11, 2019
    Hello everyone. My first post here.
    I’m working on a interesting problem with a ‘71 Commando production racer. The bike is very original, one owner, low mileage, never raced. These days it gets ridden 2-3 times a year. In the last few years the bike will start and run fine but come to a dead stop after about 10 miles. It can’t be kick- or bump-started until it sits for 30 minutes or so. Then it starts and runs fine again. This is surely an electrics issue as there’s no fuel starving exhibited when it halts. The bike is well tuned - timing,plugs, air cleaner, etc. After several episodes of this the owner put a Boyer Mk III ignition on the bike. So now it starts more easily but still exhibits the same problem.
    Before I replace the entire wiring harness or something equally drastic, has this happened to anyone else? 2MC capacitor nor zener diode have ever been replaced but symptoms don’t seem to reflect failures there. Battery is fresh and charging system is working properly.
    Thanks in advance.
     
  2. kommando

    kommando

    Joined:
    May 7, 2005
    Did you fit new coils with the Boyer, I have had several over the years that would fail when hot and then work after a cooling period.
     
    Cowboy Don and MexicoMike like this.
  3. Beach

    Beach VIP MEMBER

    Joined:
    Aug 27, 2013
    Have you checked the plugs for soot? I had Norton do the same thing and it had worn out needle jets. I also checked everything electrical before finding the problem.
     
  4. Craig

    Craig VIP MEMBER

    Joined:
    Dec 20, 2005
    Coils maybe over tightened , heat expansion cause failure ?
     
  5. Bernhard

    Bernhard

    Joined:
    Apr 20, 2011
    Vent hole in fuel tank cap blocked?
     
    MexicoMike likes this.
  6. jbruney

    jbruney

    Joined:
    Jan 5, 2019
    I installed a Wassell ignition last year & had developed some missing at higher revs. along with engine shutting down when hot. Anyway installed some new coils and the shut downs vanished only leaving minor missing for trouble shooting. Mine also started right up after a cooling period, but since there were multiple issues I can't just point the finger at the coils though I believe they were complicit. My spark wasn't very intense and with the new ones it is very bright.
    A pair of coils is not expensive and goes a long ways in eliminating the items from the list, and taking their age into consideration is another factor making them suspicious.
     
  7. Danno

    Danno

    Joined:
    Feb 7, 2010
    I have a spare pair of coils if you want to experiment.
     
  8. 1up3down

    1up3down

    Joined:
    Jan 12, 2011
    Boyer Mk 111 requires either resister spark plugs such as NGKBPR7ES with the R being resister or resister plugs wires

    did the previous owner also do this in addition to installing the new Boyer?

    also, is the Boyer mounted in a location of good air flow?
    it can shut down in self defense if overheated and 10 miles can do that

    just some ideas
     
    Last edited: Aug 12, 2019
  9. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    Boyer MkIII DOES NOT require resistor caps, plugs or wires/leads.

    http://www.boyerbransden.com/faq.html
    "Why Do I Need To Use Suppressed Plug Caps?
    MKIII and MKIV do not require suppressed plug caps for operation although we recommend using supressed 5000 ohm plug caps. Micro Digital and Micro Power units must be fitted with supressed plug caps. Plug caps fitted with suppression resistors are usually fitted to prevent radio interference. Radio interference (noise) can cause more complex electronic circuits like radios and computers to malfunction."
     
  10. 1up3down

    1up3down

    Joined:
    Jan 12, 2011
    I stand corrected, suppressed and not resister as I wrongly stated

    thanks for that LAB, I thought they were/did the same thing
     
  11. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    The Boyer MkIII (or MkIV) doesn't require resistors (caps, plugs, leads) for suppression.

    http://www.ngksparkplugs.co.za/products/ngk-resistor-caps/
    "Plug covers are manufactured to suit many applications and many are of the resistor type which provide electrical noise suppression across all frequencies whilst engine performance is not adversely affected."

    So, resistors are recommended for MkIII & MkIV but they are not required.
     
    Last edited: Aug 12, 2019
  12. Craig

    Craig VIP MEMBER

    Joined:
    Dec 20, 2005
    Yup , I have Boyer mk4 in use no suppression/resistor in circuit ,works great with champion or NGKBP7es plugs ,
     
  13. maylar

    maylar VIP MEMBER

    Joined:
    May 13, 2007
    Was the points ignition in use before the Boyer? If yes, then a coil problem would have affected only one cylinder. The only thing common to both cylinders would be the ballast resistor (not used with EI) and the kill switch.
     
  14. htown16

    htown16

    Joined:
    Apr 29, 2009
    I had a similar problem on the Trident. Run good for about twenty minutes or so then splutter out. Turned out wire from alternator was down to a few strands at connection. Would start out with full charge off charger but battery would gradually run down. Given a little time to recharge itself it would eventually restart. Take a voltmeter with you and check battery voltage when it has the problem or else give the charging system a good checking over.
     
  15. Craig

    Craig VIP MEMBER

    Joined:
    Dec 20, 2005
    Both the coils on my bike had been equally overtightened by previous owner .... have seen same thing on another bike both coils squeezed way too much .... just sayin coils “could” be problem , similar symptoms only after hot would they fail ..
     
  16. zotz

    zotz

    Joined:
    Jul 15, 2007
    Don't know whether your running an ammeter or not but I had the same issue and it was caused by a defective unit. Easy enough to bypass if you need to check it.
     
  17. M2TOY

    M2TOY

    Joined:
    Aug 11, 2019
    Thanks all for the good brainstorming. The weird thing about this is that it's happened for several years, and happened when the bike ran on points/old coils and then again after the Boyer and new coils were installed.
    Regardless, I'm going to check coils, even though they were installed new with the Boyer box. I will also give the charging system a thorough going over, starting with the voltmeter check for proper charging, then maybe have a good look at each connection in the charging circuit. I'm intrigued with the suggestion of the kill switch so that will also get a thorough look.
    Thanks again.
     
  18. storm42

    storm42 VIP MEMBER

    Joined:
    Jul 20, 2011
    I am with Bernhard and MexicoMike, blocked fuel cap.
     
  19. Chuck_Wagon

    Chuck_Wagon

    Joined:
    May 12, 2011
    That’s certainly a possibility.
    Try the simple things first M2TOY, after it quits when hot, pop open the gas cap and close it again and see if it starts up.
     

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