1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Mk3 Head RH4 require Spherical seat and collet?

Discussion in 'Norton Commando Motorcycles (Classic)' started by p400, Apr 20, 2019.

  1. p400

    p400 VIP MEMBER

    Joined:
    Jul 14, 2014
    I have taken apart 2 Mk3 exhausts with non cross over pipes and neither had the spherical seat and collets.
    Parts book calls for such along with "short" exhaust ring nuts.

    Group26Exhaust.jpg
     
  2. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004


    Non-cross over 850 pipes were not original but they are available so could be either 750 ('long' nuts and sealing washers) or intended for early 850 ('short' nuts, collets and washers) if not the 'flared' Mk3* type (with spherical seats and collets).


    *(and Mk2A according to the 2/2A parts supplement)
     
  3. htown16

    htown16 VIP MEMBER

    Joined:
    Apr 29, 2009
    No need to change them. Likely they are non balanced 750 pipes and have the longer 750 nuts which work fine in an r4 850 head. I'm using the same combo. When I get out to the shop I'll measure the length of the 750 nuts and post it so you can confirm that is what you have.
     
  4. dynodave

    dynodave

    Joined:
    May 28, 2003
    LH 1949-1972 all NHT small fin, long thread D12/167, 18092, 06-2464
    center 1973 750 big fin, long thread 06-3555
    RH 1973-1975 850 big fin, short thread, 73/74 both straight collet/ washer or 75 spherical seats and tapered collets
    [​IMG]
     
    Last edited: Apr 22, 2019
    p400 likes this.
  5. htown16

    htown16 VIP MEMBER

    Joined:
    Apr 29, 2009
    The threads on the 750 nuts are 3/4" approximately in length. Part number 06-2464.
     
  6. p400

    p400 VIP MEMBER

    Joined:
    Jul 14, 2014
    Here is what was holding the "as found" non balanced pipes.

    20190422_RemovedPipeNut.jpg
     
  7. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    Last edited: Apr 23, 2019
  8. p400

    p400 VIP MEMBER

    Joined:
    Jul 14, 2014
    This pipe had this copper "gasket/collet" the other side had none.
    Seems to be a copper ring stuck to the end of both.

    I will look closer, maybe this is a steel washer up against the end flange.
    Yes, I believe there was a copper gasket that fell out, or was jammed, of all exhaust ports.


    20190422_RemovedPipeNut2.jpg
     
  9. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    A complete bodge-up then, by the looks of it? ;)

    Could what appears to be a "steel washer" actually be the lip of the spherical seating? Edit: Or, do you mean the washer is on the nut side of the flange?

    https://andover-norton.co.uk/en/shop-details/16482/ex-pipe-spherical-seating
     
    Last edited: Apr 23, 2019
  10. MichaelB

    MichaelB VIP MEMBER

    Joined:
    Jan 14, 2004
    Measure the thread length of the nut.
    5/8" equals 850 nut which needs collet.
    3/4" equals 750 nut, doesn't need collet.

    The shorter one needs collet as you run out of threads.

    Or use double washer at port.
    Steel washer behind conical washer will work, though not correct...

    If you are buying new header nuts, and running unbalanced pipes, get the 750 nuts with the 3/4" depth.
    More thread into the head..
     
  11. dynodave

    dynodave

    Joined:
    May 28, 2003
    Normal 500 thru 750 plain machined flare, use with long nut, use head washer in port, Avoid rattle ring locks... as museum pieces only.
    Cheap aftermarket pipes may not even have fully machined stub with flange. Original norton pipes were angled and is why Real Norton factory pipes fit with out hitting kick start. Almost all after market pipes come straight out of the port and are the main source of kick start problems.

    [​IMG]

    Normal 850 SQUARE collet pipes. Use washer on head.
    [​IMG]
    Normal MKIII sphere type. Shown on left is garbage AFTERMARKET no balance pipe used for holding dyno thermocouple. MKIII collets have proper bevel to mate to pipe flare, one piece or split will work OK. These flare pipes NEVER go in port without spherical cone.
    IDIOTS will just put a gasket in the port and crush the hell out of it, flattening the flare....damage the port bottom?
    [​IMG]
     
    Last edited: Apr 24, 2019
    chaztuna and MichaelB like this.
  12. MichaelB

    MichaelB VIP MEMBER

    Joined:
    Jan 14, 2004
    Good stuff Dave.
    Didn't realize the collet was machined to interact with the flare as such.
    Need to reexamine how the longer nut interacts with the flare.

    It seems most current pipes are flared, Mark 3 style.
     
  13. dynodave

    dynodave

    Joined:
    May 28, 2003
    Any pipe with collets should NOT use long exhaust roses. You loose 2 threads of engagement.
    Only square flanges uses long nuts.
    I wonder if parts sellers even know what they are selling??? and can steer guys to the right combination of parts.
     
  14. MichaelB

    MichaelB VIP MEMBER

    Joined:
    Jan 14, 2004
    Yes, I get the part about the colletts being used with the short roses.

    What has become clear today is the short roses with the later Mk 3 collet, # 06.6520, with the spherical washer should be used on all Belled pipes, balanced or unbalanced.
    Short roses with Colletts # 06.3990 with steel or copper washer should be used on earlier/original square type (non belled) balanced pipes, these flanges have cut outs for the correct colletts.
    Long roses with steel or copper washer should be used on unbalanced, square type (non belled) flanges.

    It's the flange that determines the correct Rose/collett, not balanced or unbalanced.


    Like I said, Good Stuff Dave and thanks......
     
    Last edited: Apr 23, 2019

Share This Page