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Runs well, plugs foul....

Discussion in 'Norton Commando Motorcycles (Classic)' started by Lineslinger, Mar 30, 2019.

  1. CanukNortonNut

    CanukNortonNut

    Joined:
    Aug 8, 2005
    I use tickle and choke to start my bike when cold. I also cut my fuel tap 1/4 mile from home when I put her to bed. But that just works for my bike.
     
  2. Mwood7800

    Mwood7800

    Joined:
    Jul 26, 2017
    Double check the timing.
     
  3. acadian

    acadian VIP MEMBER

    Joined:
    Mar 5, 2010
    OP said he set timing via degree wheel, so I'm just assuming he's already verified the timing gauge marks are correct (or most likely off)
     
  4. Lineslinger

    Lineslinger VIP MEMBER

    Joined:
    Feb 26, 2017
    8E37C523-8A64-4E09-B212-D98C2FF4200A.jpeg

    Photo displays getting setup.
    Timing good, thank you for the attention guys.

    After I install new floats I am going out to the airfield and run some plug chops on a tank of 100 octane aviation fuel (no ethanol) with a hotter plug and needles in leanest setting. I can do this without getting into the main jets....
    Should help get a better understanding of where it is and next step.
    I’m still hoping it is just a straight forward float bowl adjustment at fault.
     
    Last edited: Apr 2, 2019
  5. acadian

    acadian VIP MEMBER

    Joined:
    Mar 5, 2010
    Great, when you set the degree wheel at 28 BTDC, where does the timing mark on the rotor land in relation to the gauge in the primary cover? In my case the primary gauge is 4 degrees off...
     
  6. ashman

    ashman

    Joined:
    Jul 11, 2010
    Well my 1974 850 Commando stock jets were 260 main jets and I have owned the bike since new, but with the work done to my motor I up the main jets to 270, in my workshop manual it said the same the M111s have 220 main jets so 220's aren't standard for the 74 850 Commando, but these days I am running PWK carbies but am thinking about going back to the Amal's.

    Ashley
     
  7. pommie john

    pommie john

    Joined:
    Nov 18, 2005
    It seems you've done everything you should, all the logical things. Time to think about illogical things. I was once sold the wrong slides. Is the number on the bottom of the slide the same as the old ones? Could you have been sold richer slides?

    Also, back to my previous comment about a small amount of oil burning turning the plugs black, is there any blue smoke? Just a hint of it when you give it a rev? Could be rings?
     
  8. Danno

    Danno

    Joined:
    Feb 7, 2010
    A good strobe shot on the ignition wouldn't hurt, either. Good way to check the advance curve.
     
  9. dave M

    dave M

    Joined:
    Oct 19, 2005
    Try running it without the air filter and see if it helps, there have been reports over the years of people having difficulty setting up the carbs with these filters.
     
  10. Lineslinger

    Lineslinger VIP MEMBER

    Joined:
    Feb 26, 2017
    The inner primary reference gauge was off by less than 1 degree in relation to the rotor.
    Hard to believe, maybe another comparison in order.
    I used an electrical meter and a TDC reference indicator to locate my true TDC. Damn close if not dead on.
     
    Last edited: Apr 2, 2019
  11. Lineslinger

    Lineslinger VIP MEMBER

    Joined:
    Feb 26, 2017
    I installed new slides during overhaul. Sizing matches.
    No smoke. Head redone. Cylinders honed with new rings and properly seated.
    It’s a mixture issue thus looking at your observation “illogical things” as where to go next if my little bit of testing doesn’t work out.
     
  12. Lineslinger

    Lineslinger VIP MEMBER

    Joined:
    Feb 26, 2017
    After new floats go in next step Dan.
     
  13. Lineslinger

    Lineslinger VIP MEMBER

    Joined:
    Feb 26, 2017
    Huh, the K&N is all about more air and I have not put any oil on it yet, too new.
    Something to think about.
     
  14. dave M

    dave M

    Joined:
    Oct 19, 2005
    Lineslinger, I only mention this because it is such a quick thing to check and I recall that not all previous reported issues were related to too much oil in the filter.
     
  15. Dances with Shrapnel

    Dances with Shrapnel VIP MEMBER

    Joined:
    Jul 8, 2011
    You might want to do a side by side comparison of the slide cutaways or measure the slide cutaways. I’ve seen things mis-marked and incomplete manufacturing before.
     
    Last edited: Apr 3, 2019
  16. Lineslinger

    Lineslinger VIP MEMBER

    Joined:
    Feb 26, 2017
    2A1DCA3F-2ED7-45FA-BB96-8BA778BDC83E.jpeg 1663A27F-215B-48C8-9EE6-7E9DCF425C08.jpeg AFA5505C-93CF-4056-963C-AAEC51B9F8DE.jpeg Measuring/comparing is a good thought which I did upon installing the new slides.

    Thank you for the attention.
     
  17. Lineslinger

    Lineslinger VIP MEMBER

    Joined:
    Feb 26, 2017
    It’s a good idea.
    When I first received it I blew out the filter from the inside with compressed air just to be sure too much oil was not impregnated in the filter medium. I over oiled a K&N dual quad filter once and this cleared it. The new Filter for the Norton was as as it should be.
     
  18. dynodave

    dynodave

    Joined:
    May 28, 2003
    Post#10
    you show only a muffler.
    What is the exhaust system?
    850 balance pipe? Carb tune is different than individual 750 style pipes. Air cleaner affect it too.

    I run BP6ES in my MKIII. Same plugs for over 3 seasons. Runs like a top
     
  19. jbruney

    jbruney

    Joined:
    Jan 5, 2019
    Wish my carbs was that purty. That gremlin is fast running out of hideouts. There's something hiding in them. I don't know what or where, but I'm more than sure it's in them. Sorry for thinking out loud.
     
  20. 1up3down

    1up3down

    Joined:
    Jan 12, 2011
    wow, this is a real problem to solve

    I will take one more shot, maybe maybe the choke slides are not fully retracted and are letting in enough of a richer mixture to cause the fouling?

    question: it is possible the choke is left on too long after cold start?
     

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