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New Inner Chaincase Touches Swingarm

Discussion in 'Norton Commando Motorcycles (Classic)' started by marshg246, Mar 11, 2019.

  1. marshg246

    marshg246 VIP MEMBER

    Jul 12, 2015
    I installed a new inner chaincase from AN on the 74 850 I'm rebuilding and carefully got the center stud shimming right. While doing the oil hoses and horn, I noticed that the swingarm appeared to be touching the chaincase. A piece of paper will fit between them except in one spot. Of course, I have the entire primary done.

    It would be easy to relieve a little from the chaincase before installing. So, if you're installing a new one it would be good to check before finishing the primary.
  2. bill


    Jun 1, 2003
    i have seen witness marks on old ones also and they were properly shimmed.
  3. kommando


    May 7, 2005
    I have also seen polished inner chaincases where the swingarm outer cover has rubbed on the cover. Not much clearance there and with all the tolerance build ups over long distances surprised it does not come up more often. Try 2 gaskets on the crankcase joint and reshim to suit.
  4. concours

    concours VIP MEMBER

    Dec 29, 2011
    Iso install sequence is all good, adjusted, bolt tightened?
  5. grandpaul

    grandpaul VIP MEMBER

    Jan 15, 2008
    I've seen marks on probably 90% of the 20+ Nortons I've rebuilt, gouges on about 25% of them, and 3 or 4 with serious cracking from improper shimming.
  6. marshg246

    marshg246 VIP MEMBER

    Jul 12, 2015
    Did a little investigating. My unrestored 74 MKIIa has almost no clearance - maybe .005". The 72 I recently rebuilt has a noticeable gap. I thought it was the new chaincase, but I guess it is something about the 850. Since there should be little to no movement side to side there, it would probably be OK, but I'm going to take it back apart and relieve that area on the back of the chainchase slightly. While harder to do than adding a second gasket, it seems like a better fix to me.
  7. dynodave


    May 28, 2003
    Engine attaches to swing arm through the rear engine cradle. ISO's not involved.
    Run with loose engine bolts?
    Engine pulls itself toward rear on chain side! Chain case (attached to engine) gets pulled/swings into collision with first item....swing arm. Limited only by central post.
    Old used cradle with damaged holes? Holes worn bigger on left?
    Cradle bent?
    powder coat yielding?

    NEW AN primary?
    Did you check if enough clearance possible prior to assembly. Measure, verify, then use.
    Last edited: Mar 12, 2019
    nortriubuell likes this.
  8. Craig

    Craig VIP MEMBER

    Dec 20, 2005
    Just like you do with every bearing ...
  9. marshg246

    marshg246 VIP MEMBER

    Jul 12, 2015
    I finally got back to working on this. To make sure the engine wasn't somehow twisted in the cradle, I loosened the engine mounting bolts and tried to pull the inner chaincase away from the swingarm. That accomplished nothing. So, as several have suggested, I'll put it back together with two gaskets. The gaskets I have from AN are .021" thick - that will certainly fix the swingarm clearance problem (red oval).

    While investigating this problem, I noticed the master link is hitting the seal plates (blue oval).

    Originally, I thought that relieving the cover where it meets the swingarm was all that was needed, but the master link problem is much bigger. I don't know if two gaskets will fix the master link problem but installing it from the outside in will if not. Yes, it is a standard chain, not o-ring and not heavy duty

    2 - Building - Primary 4.jpg
    nortriubuell likes this.
  10. kommando


    May 7, 2005
  11. marshg246

    marshg246 VIP MEMBER

    Jul 12, 2015
    I installed two gaskets and rechecked everything. The swingarm clearance is resolved and the chain itself was fine, but the master link, when installed normally was very close to hitting the seal plates and with any deflection while riding, it would hit. So, I searched and found some 10B-1 chain (British Standard).

    Until I started researching this I didn't realize that British Standard chain is also called Metric Chain. Nominally, 10B-1 and ANSI 530 are the same, but 10B-1 is not as wide and the master link is a good bit narrower. Of course this is nothing new to many on this forum. Once I started searching by Metric Chain, I found plenty of suppliers and ordered from one. The overall width of the ANSI chain master link was .870" and the 10B-1 is .824" so problem solved.

    So my research isn't wasted and because plenty of others are asking similar questions, I've started documenting chains and what I found here: http://www.gregmarsh.com/MC/Chains.aspx - I'm clearly not an expert on this subject so if you find something wrong or have something to add, please let me know.

    BTW, I bought 50' of the 10B-1 chain and I have a supply of half links and master links so if you're fighting this problem, PM or email me.
    swooshdave and nortriubuell like this.
  12. gortnipper

    gortnipper VIP MEMBER

    Nov 11, 2013
    Just call you Greg "the Chain Man 2". :D
  13. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Nov 20, 2004
    Edit: Link works now.

    Not exactly the same, as it is ANSI 50 or 10A-1. Not only is the side plate thickness and overall width different but also the inside width.


    "European (BS) Standard - Simplex
    10B1,10B-1, 0.625,15.875, 9.65, 10.16, 14.60, 1.55, 1.55, 5.08, 18.8, 2.5

    ANSI Standard - Simplex
    50A1, 50-1, 0.625,15.875, 9.40,10.16, 14.60, 2.04, 2.04, 5.08, 20.4, 2.7
    Last edited: Jun 13, 2019
  14. marshg246

    marshg246 VIP MEMBER

    Jul 12, 2015
    Bad idea! After 50+ years owning and working on British motorcycles, I know almost nothing about chain specifications - I just want the darned things to do their job and not bang into other parts of the bike! :( Hopefully, by doing a little documentation, I can relieve others from having the chain pain I've been having lately!
    Niagara850 and HRD like this.
  15. ClassicChainsGuru


    Jul 20, 2016
    Hi All. Just came across this thread & encouraged to see others taking a healthy interest in chains. There are too many so called anecdotal "facts" being peddled around so it's always refreshing to see someone taking the time to do some proper research.

    I work for Renold having started as an apprentice in 1983 & am regarded as the motorcycle chains guru here. I don't know everything but if I can help with anyone's chain related issues, especially regarding Renold, I'm happy to help where I can. I have access to just about all the motorcycle chain records from the year dot & do actually know what's made & where. I can't go into detail on future plans right now but will be happy to provide any information on historical bike chains.
  16. Matchless


    Dec 23, 2010
    Hi CCG,
    Is Renold chain & in particular the motorcycle chain still made in England. Also, are there any plans to start making O ring chain again?


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