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Atlas Header pipes

Discussion in 'Other Norton Motorcycles' started by possm, Mar 14, 2019.

  1. possm


    Jul 3, 2009
    Hi Guys I am restoring a 1966 Atlas and I note looking through the Roy Bacon Norton Restoration book that period photo's appear to show the Atlas (and 650SS) with 1-1/2" diameter Header pipes. I note that Andover, Armours Feked etc only offer the 1-3/8" alterative, I am aware that the Commando came out with 1-3/8 pipes std, is there an advantage in either? I think I prefer the look of the 1-1/2 pipes though am unsure who supplies a quality set.

    Thanks Al
  2. Mike B

    Mike B

    Oct 16, 2015
    I believe U.K. home market bikes came with 1 3/8 pipes, while U.S. export bikes came with 1 1/2 pipes. Their seems to be a consensus that the bikes run better with the smaller pipes...don't know from personal experience, but I prefer the smaller pipes.
    Mike B.
  3. Gilesy

    Gilesy VIP MEMBER

    Aug 27, 2017
  4. possm


    Jul 3, 2009
    Thanks Gilesy, I made the mistake of buying a set off RGM when I restored my 650SS, didn't even look like fitting, had to heat bend and re chrome, I complained to RGM as I am half a world away and of course "they had never had a problem before".
  5. nortonmark


    Oct 18, 2018
    Well as they all say “bigger is better” who?
    That’s why all tuners go big on exhaust pipes now days and I think that’s why the Atlas came with 11/2 pipes
    I ran fat pipes and later Comando pipes on my Atlas, the bigger exhaust pipe gave me better juice
  6. texasSlick

    texasSlick VIP MEMBER

    Jan 2, 2013
    Americans like fat pipes. Fat pipes exude the illusion of power. That is likely the reason the Atlas came with 1 1/2" pipes in the US market.

    The 1 3/8" pipes may (may means I do not know for sure) provide more torque at some particular rpm .... that is, they are tuned.

    Honda solved the problem of skinny, but tuned pipes, and made them attractive to the American market, by putting the skinny pipes inside larger ones. That solved the blueing problem as well.

  7. Bernhard


    Apr 20, 2011
    For the 750 I would be inclined to use stepped pipes, 1.5 at port, tapering down to 1.375 –at silencer it goes up to 1.5 again.

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