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Possible to adapt later exhaust to earlier head?

Discussion in 'Norton Commando Motorcycles (Classic)' started by 998cc, Apr 13, 2019.

  1. 998cc

    998cc "Cheap" is rarely the least expensive. VIP MEMBER

    Joined:
    Oct 1, 2018
    Good day folks. My bike is a 74 model produced in September of 73. I ordered and received what I thought was the correct set of exhaust header pipes, but they are the later version. Is it possible/practical to adapt these to my Commando, or do I need to send them back for the correct set?

    Thanks.

    ~998cc
     
  2. oldbeezer

    oldbeezer VIP MEMBER

    Joined:
    Nov 2, 2017
    I no expert but I think so. In the not too distant future I will be going the other way. 750"S" system on a 850 MKII
     
  3. 998cc

    998cc "Cheap" is rarely the least expensive. VIP MEMBER

    Joined:
    Oct 1, 2018
    Here are a couple of photos.

    The new unbalanced pipe.
    IMG_0401.JPG


    The existing balanced pipe has a conical flange.
    IMG_0403.JPG


    ~998cc
     
  4. sportsroof

    sportsroof

    Joined:
    Mar 4, 2014
    Seem to recall I did this back in the late 70's when parts were scarce. 850 balanced system onto 750 engine, recall split collets at the head end of the pipes, locked in by the threaded retainers as per 750 system. Don't blame me if I'm wrong.
    Cheers, Martin
     
  5. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004

    That's 'earlier'.


    That's 'later'.
     
  6. L.A.B.

    L.A.B. Moderator VIP MEMBER

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    Nov 20, 2004
  7. 998cc

    998cc "Cheap" is rarely the least expensive. VIP MEMBER

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    Oct 1, 2018
    Thanks L.A.B. This is really good information. :)
     
  8. 998cc

    998cc "Cheap" is rarely the least expensive. VIP MEMBER

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    Oct 1, 2018
    Thanks L.A.B. for the link to the earlier thread. From the info in the thread, the AN website, and comparing to what is installed on my Commando, it looks like my exhaust is Mk-III, but the hardware it was installed with is incorrect for the pipe flange. Flat sealing washers (not conical) were found. See photo:
    IMG_0406.JPG

    It looks as if the new pipes I have may be correct for the bike and will work with the existing hardware--collets and short nuts (the thread depth of the nut measures +- .575"). Can anyone provide some insight on this and possible differences in pipe bends downstream?

    ~998cc
     
  9. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    Often referred to as 'Mk3' pipes but also listed in the Mk2/2A supplement for the Mk2A.


    Yes.
     
  10. 998cc

    998cc "Cheap" is rarely the least expensive. VIP MEMBER

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    Super!! Thanks L.A.B. and the forum!

    ~998cc
     
  11. Fullauto

    Fullauto VIP MEMBER

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    Apr 13, 2009
    I thought all 850s came with the balanced pipe. In fact, I'm sure of it.
     
  12. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004

    I wasn't saying unbalanced pipes are, or were, "correct".

    998cc said: "It looks as if the new pipes I have may be correct for the bike and will work with the existing hardware--collets and short nuts (the thread depth of the nut measures +- .575")."

    So "correct" in the sense that the new pipes will work with the existing hardware and why I replied "Yes".
     
    Last edited: Apr 13, 2019
    Fullauto likes this.
  13. 998cc

    998cc "Cheap" is rarely the least expensive. VIP MEMBER

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    Oct 1, 2018
    Gentlemen.
    Whatever the case, I appreciate the sharing of your knowledge in helping this longtime Norton aficionado (with little Norton mechanical experience) avoid making the mistake of sending back the technically correctly fitting (though non-balanced) pipes and then ordering the technically wrong ones for the hardware.

    Sincerely,

    Russ
    ~998cc
     
  14. Danno

    Danno

    Joined:
    Feb 7, 2010
    If you disregard the different performance aspects of different diameters, balanced or no etc., you can swap just about any Commando pipes for any others with the proper small parts. Some of the rosettes have less thread and length than others depending upon the sealing system (collets, crush washers and/or conicals). Balanced pipes need split collets or there would be no way to get the rosettes on.
     
  15. 998cc

    998cc "Cheap" is rarely the least expensive. VIP MEMBER

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    Oct 1, 2018
    Thanks Danno. Yes, that is becoming apparent! :) Interestingly, the new unbalanced pipes require the collets to be used. No worries though; it will be a better installation than what was just removed from the bike.

    The learning continues. :)

    ~998cc
     
    Last edited: Apr 14, 2019

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