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Inner Chaincase Sealing Disc Failure

Discussion in 'Norton Commando Motorcycles (Classic)' started by Dellis, Nov 24, 2019.

  1. Dellis

    Dellis VIP MEMBER

    Joined:
    Jul 22, 2018
    Riding a long last week my bike started to make a strange catching noise, I pulled over and it stopped so I pulled off and it came back, I pulled over and investigate. Rotating the rear wheel made a rubbing noise coming from the back of the gearbox. I got down and poked my head underneath to try and see what was going on , it's not easy to sse but I could see something between the front sprocket and the inner primary but couldn't make out what it was so common sense took over and I jumped on the back of my pals bike to go and get my trailer.

    So yesterday I pilled the primary apart and the issue was that the spot welds on the sealing disc had failed and the half between the primary and front sprocket had been chewed up by the chain. Looking on both RGM and Andover the discs are unavailable however I found them at Norvil and have ordered a replacement. Only issue is they are spot welded and I don't have access to a spot welder so I've decided to drill four holes in one of the plates where the spot welds would be located, clamp them together (I've turned a couple of alloy bits to achieve this today), and then mig weld the two halves together. This will be next weekend and I'll update on the results after my efforts.

    Dave
     
  2. comnoz

    comnoz VIP MEMBER

    Joined:
    Dec 10, 2008
    Or 6 little screws and nuts and a little locktite work too.
     
    SteveA likes this.
  3. texasSlick

    texasSlick VIP MEMBER

    Joined:
    Jan 2, 2013
    Little screws, nuts, and loctite is how I did mine. If I should ever have to remove my inner primary cover again, I will investigate installing a lip seal between the disks. I have stopped all the primary case leaks except a small weep past the discs along the transmission shaft.

    While you are in there, you might consider the modification between the discs which I did to suppress oil leaks ....https://www.accessnorton.com/NortonCommando/how-to-make-the-atlas-dominator-primary-oil-tight.26860/

    Slick
     
  4. o0norton0o

    o0norton0o VIP MEMBER

    Joined:
    Apr 27, 2015
    You could also make a spot welder out of an old microwave oven... :cool: I think I spent less than $50. to make it. It turns 120volt/15 amps into ~ 40volts/800amps (I forgot the exact figures) You could find the instructions to make it on Youtube if you search. I made it after I finished making the capacitor powered spot welder I needed to rebuild NiCd battery packs.

    microwave spot welder1.jpg
     
  5. concours

    concours VIP MEMBER

    Joined:
    Dec 29, 2011
    Drill one half with 1/8” holes plug weld using whatever welder you have access to. (MIG, TIG, gas weld, braze) doesn’t take much.

    I’d be looking for WHY that seperated...
     
  6. olympus

    olympus

    Joined:
    Aug 5, 2017
    Drill & screw the two halves together with 6 M3 screws/ nuts with a dob of Loctite... easy peasy task to fit and compress the felt washer
     
  7. Dellis

    Dellis VIP MEMBER

    Joined:
    Jul 22, 2018
    I've already looked at the two halves and I have to say I'm amazed they held together for so long. The inner disc has a 'slinger' fitted and the weld had penetrated through the 'slinger' and the inner disc but you can only just see the slightest mark on the outer disc where the weld should have penetrated so my conclusion is that the initial spot weld had insufficient penetration to properly weld the three layers together.

    Dave
    To be honest mine doesn't leak from the back of the primary so I will reassemble as it subject to fixing the plates together.

    Dave
     
  8. Dellis

    Dellis VIP MEMBER

    Joined:
    Jul 22, 2018
    Thanks for all the replies. Food for thought with the nuts and bolts ideas, I did think about this but thought the weld might be a better job although with nuts and bolts you can seperate the two halves but I'm not sure why I'd want to... Thoughts?

    Dave
     
  9. texasSlick

    texasSlick VIP MEMBER

    Joined:
    Jan 2, 2013
    To replace the felt washer at some future time?

    Slick
     
  10. Pushed it n rode it

    Pushed it n rode it

    Joined:
    Jun 10, 2019
    I have the infamous pressed steel dommie chain case with twin washers and felt. Not sure if it's quite the same on a commando but I drilled and soft rivetted mine. Next change, drill out rivets and renew. Maybe different for you big boys. !!
     
  11. Dellis

    Dellis VIP MEMBER

    Joined:
    Jul 22, 2018
    I've just been out to have a look and with the 'slinger' attached then the bolts heads would have to be tiny, as tiny as 8 ba, and i'm not confident in that as a fix so I've decided to stick to plan a and weld them together. I've changed the felt seal before when the plates we attached to one another, it would be easier if the plates could be separated but it's not that difficult when they're together.

    Dave
     
  12. Dellis

    Dellis VIP MEMBER

    Joined:
    Jul 22, 2018
    I do like that.

    Dave
     
  13. Mwood7800

    Mwood7800

    Joined:
    Jul 26, 2017
    I used pop rivets and then sealed the holes. Also I shimmed the case for better alignment
     
  14. Dellis

    Dellis VIP MEMBER

    Joined:
    Jul 22, 2018
    Parts arrived and as I said decided on welding the plates which is what I did, all is now back together.

    Dave
     

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