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Rear wheel & chain clearance question

Discussion in 'Norton Commando Motorcycles (Classic)' started by emubritish, Oct 23, 2019.

  1. emubritish

    emubritish

    Joined:
    Oct 21, 2019
    Hi,

    I am finishing up a rebuild of a '72 commando that was provided to me in boxes, so I have never seen the bike assembled.

    An issue I am having is that with the rear wheel installed, the chain rubs the outside of the chain guard, even when the wheel is tight in the frame.

    The bearings were never pulled from the hub as they were in great shape, and the other pieces appear to be assembled in the correct order according to the diagrams on andover norton and old britts websites.

    I have noticed a 4-5mm gap between the back of the sprocket/brake drum and the wheel hub - I replaced the cush drive rubbers and am curious if this is just not fully seated. I have gone to town with a breaker bar on the axle nuts and the rubbing improves, but the quick link still catches the guard and I am sure I am severely over-tightening the axle.

    Any hints or suggestions would be greatly appreciated. The only other comment is that I have to spread the rear end slightly to get the spacer on the outside of the speedo drive to fit, which is part of the reason I think the brake drum is not fully seated.

    Thanks,
    Chris
     
  2. Danno

    Danno

    Joined:
    Feb 7, 2010
    If you have the standard 19" rear wheel, no way it should be rubbing the chainguard. It's either waaaaayyy out of line with the front or something was assembled in the wrong order. The Titanic has a small gap between the brake drum and wheel hub, but new cushes can make things a little tight. Commandos are also known for imperfect rear wheel to rear fender alignment, so don't let that throw you off. There should be a fairly equal gap between the tire and both sides of the swingarm.
     
  3. MichaelB

    MichaelB VIP MEMBER

    Joined:
    Jan 14, 2004
    Mine is extremely tight also.
    If it’s just the master link hitting you can turn it around so the clip is on the inside.
    Or, go to a riveted master.
     
  4. Pushed it n rode it

    Pushed it n rode it

    Joined:
    Jun 10, 2019
    I have always used the joining link clip on the tyre side with my Dommie, the dreaded pressed steel primary chain case doesn't give enough clearance. A very old friend also does it on his 850 MK2 A.
     
  5. maylar

    maylar VIP MEMBER

    Joined:
    May 13, 2007
    Problem with that is that the master link pins can (probably will) hit the gearbox case.
     
  6. Pushed it n rode it

    Pushed it n rode it

    Joined:
    Jun 10, 2019
    Never happened in 42 years, but the gearbox sprocket did come loose on the lock washer and caused me and it to wobble ! A few aluminium shavings but still knocking up the miles
     
  7. jsnorton

    jsnorton

    Joined:
    Oct 10, 2018
    Are you sure the chain guard is positioned properly, may need shimming out.
     
  8. batrider

    batrider

    Joined:
    Aug 9, 2008
    Check that the bolt used to mount the rear shock (and slot in chainguard) has a thin head. If not, it can force the chainguard in. Nut should be on the outside.
     
    Last edited: Oct 24, 2019
  9. illf8ed

    illf8ed

    Joined:
    Dec 30, 2003
    Hi Chris,

    My '72 also has the very close fit from chain to the outer part of the chainguard. The chain has hit the rear of the guard and left a mark. Your situation is not unique. I suppose you could add another shim on the dummy axle and that would move the drum/sprocket toward the timing side. The shim goes on the axle just inside the drum after you take the brake shoe cover off.
     
    kerinorton likes this.
  10. Tornado

    Tornado VIP MEMBER

    Joined:
    Dec 5, 2017
    I believe there were some responses in another similar thread regarding the mounting point on the guard needing some squeezing to a thinner spacing so that chain could clear. Also be sure the thin head bolt is being used to the inside of swingarm such that it slides easily into the guard mounting. Note there are two different lower shock mount bolts, one is thin headed for chainguard my 850 had these swapped when I got bike without a guard
     
  11. motorson

    motorson VIP MEMBER

    Joined:
    Nov 29, 2011
    Everybody here is talking about the rear wheel and that is where Chris said the problem was showing up. I have also measured a tenth of an inch difference in the offset of front sprockets. In other words, if your chain is hitting the transmission or primary case it could be the offset of the front sprocket causing the problem.
     
  12. Tornado

    Tornado VIP MEMBER

    Joined:
    Dec 5, 2017
    OP stated chain was hitting the outside of the chain guard, not primary.
     
  13. motorson

    motorson VIP MEMBER

    Joined:
    Nov 29, 2011
    "OP stated chain was hitting the outside of the chain guard, not primary."
    Yes, but a couple of mentions were also made of chains hitting either the primary or transmission. (I cannot, for the life of me, figure out how everyone is doing those nice little quotes of previous posts.)
     
  14. Tornado

    Tornado VIP MEMBER

    Joined:
    Dec 5, 2017
    Just use the Reply button lower right of the actual message you want to quote. Text entry should open with that message content already in quote tags.
     
    motorson likes this.
  15. kerinorton

    kerinorton

    Joined:
    Feb 12, 2013
    Thanks Tornado. I have just learned what to do with the reply to quotes.

    Both my 750 and 850 have close clearenes between the chain and outer chain guard edge. Just the way it is.

    If you use IWIS 10b chain, it should not hit the inner primary and especially with the clip on the wheel side. 530 chain is unnecessarily wider and can hit the primary. IWIS chains also last a lot longer than any other chains.

    Dereck
     
  16. 850cmndo

    850cmndo

    Joined:
    Dec 9, 2009
    What I've found is you need to have the 'oil outlet' for the chain oiler, or suitable spacer, in place with the through bolt. Without it, I've found the chain guard twists and you're apt to have the master link hit the very rear edge of the chain gaurd.
     
  17. Tornado

    Tornado VIP MEMBER

    Joined:
    Dec 5, 2017
    Regarding that chain oiler fixing point on swing arm,is there anything placed on the SA hump so that the chain doesn't slap against it when flaps up and down? Modern bike has rubber piece along SA where the may slide along it.
     
  18. 850cmndo

    850cmndo

    Joined:
    Dec 9, 2009
    If there is, I haven't seen it. I suspect you could mock something up.
     
  19. MichaelB

    MichaelB VIP MEMBER

    Joined:
    Jan 14, 2004
    Saw a post on here somewhere that referred to a washer/shim between the drum and backing plate.
    Part #21 on rear wheel page. The original parts manuel refers the quantity AR, as required. This was obviously an issue from the beginning. Tore mine down, sure enough, no washer.
    I will order some on my next order, in the mean time, anyone know the dimensions of this washer, specifically the thickness.
    Part #06.7607, old number NM5276. Must not be anything to technical as it's referred to as a 'washer', not a shim..
     
  20. HoveToo

    HoveToo

    Joined:
    Jan 1, 2012
    My chain guard was damaged by the chain hitting it on the outside when the newly fitted bearings in the brake drum moved. The circlip had not seated correctly and this allows the whole assembly to move. It might be the reason you have a gap on the other side of the brake drum. I had to slim down the circlip to ensure that it properly seated.
     

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