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Flange ring

Discussion in 'General Classic Motorcycle Discussion' started by ashman, Jan 5, 2014.

  1. ashman


    Jul 11, 2010
    Just about to start to rebuild my 650 Manxman motor but the flange ring on top of the cylyinder one side has a bit broken off the ring


    what will I need to do to fix this or do I have to resleeve the barrels or can I use it this the way?
    The bores on this motor is still good at 20thu over size.

  2. Rohan


    Aug 26, 2010
    Remind us where this motor actualy seals its head/cylinder joint.
    The flange plays no part in the actual sealing ?
    The head gasket should start to crush before the flanges touch the head. ?

    On the earlier 500cc dommies, its the headgasket between head and cylinder that does the sealing, the flange merely positively locates the head to the cylinder.
    On subsequent domies, somewhere in the mid1960s, that flange was deleted - the headbolts did all the locating, with no ill effects it seems.
    Makes surfacing the top of the cylinder much easier - which you are going to need to do ?

    You do see reports of those flanges being totally machined off.
    Although metal rings then need to be fitted into the head to substitute, and remove what would otherwise be a dead space in the combustion chamber.
  3. texasSlick

    texasSlick VIP MEMBER

    Jan 2, 2013
    Wait for Comnoz to chime in.
  4. Rohan


    Aug 26, 2010
    I intend to shave the spiggotts off some Atlas cylinders, and use them with a later head.
    As many have found, if they serve no real purpose, there is no need to keep them...
  5. B.Rad


    Feb 28, 2012
    Gidday Rohan
    I was talking to a bloke on Saturday who said he had done the same thing. Put a Commando head on Atlas barrels. he pointed out the Atlas cylinder has the 4 outside holes tapped 5/16th diameter and Commando 3/8th holes. he just puts 5/16 head bolts into the 3/8th holes. and also of course got rid of the flanges.
    Not knowing Atlas motors, is this correct. also is there any consequences from putting the smaller bolts in the bigger holes
    ride safe Bradley
  6. pommie john

    pommie john

    Nov 18, 2005
    I'd machine it off and insert a ring into the groove in the head.

    My Commando/Atlas motor was the opposite of yours.... I had an Atlas head with Commando barrels. So I had no flange on the barrels I had but the grooves in the head where the flanges were supposed to go. I had a machine shop make a couple of alloy rings that are an interference fit in the grooves in the head. The head bolts do a perfectly good job of locating the head on the barrels.

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