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Difference in front drive sprocket thickness causes rubbing on inner primary case

Discussion in 'Norton Commando Motorcycles (Classic)' started by jimbo, Apr 17, 2019.

  1. jimbo

    jimbo VIP MEMBER

    Joined:
    Sep 25, 2004
    After getting the MK3 engine in the frame, I am starting the primary assembly. I had rubbing from the sprocket and rebuilt the transmission because the sleeve gear bearing fit was loose. I still have rubbing with a different trans case and the 21 th sprocket I used before. I compared a 20 tooth I have with the thickness of the 21 tooth and found the 21 toother is much thicker causing rubbing and maybe a chain misalignment. Confused again......


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  2. concours

    concours VIP MEMBER

    Joined:
    Dec 29, 2011
    I would call that “hub offset”, based on the side view.
     
  3. Craig

    Craig VIP MEMBER

    Joined:
    Dec 20, 2005
    Pretty sure I have 22T and 19T sprockets in shed , do want thickness measurements , the 21T is on bike ....
     
  4. jimbo

    jimbo VIP MEMBER

    Joined:
    Sep 25, 2004
    As the 20 thoother fits with no rubbing I think I'll go with the 20 , as we don't run on the interstate much any more, and the bike was real happy at 65+mph but not at 55 , so I'll drop the happiness down to about 60 +. Its a big mystery , they only thing I can think of is the sleeve gear and bearing moved away from the inner primary cover enough to allow me to ride it for years that way, because the bearing fit was loose. Now that I have the bearing tight in another case it rubs more.
     
  5. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    nortriubuell likes this.
  6. justin scroope

    justin scroope

    Joined:
    Apr 17, 2019
    Had this problem back in the eighties. Turned out that the rubbing sprocket was mean,t for a featherbed.
     
  7. jimbo

    jimbo VIP MEMBER

    Joined:
    Sep 25, 2004
    funny thing is , I ran it for years on the MK3,when I removed the inner primary it showed rubbing, but not so much and I never noticed a resistance or noise.But it rubbed big time when I rebuilt the trans. So I am thinking the looseness in the old trans sleeve bearing fit allowed it to move away from the inner primary cover and the drive chain just ran where it wanted moving the sprocket away.Keeping it from rubbing. Kind of weird .
     
    Last edited: Apr 19, 2019

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