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Engine cases : are the halves matched ?.

Discussion in 'Norton Commando Motorcycles (Classic)' started by Josh Cox, Sep 29, 2010.

  1. Josh Cox

    Josh Cox

    Sep 24, 2010
    G'day ( Australian for "Wassup ?"),

    Have a 70 model commando, with 71 cases, also have the original cases ( correct No to frame ).

    Intend on matching up the frame and engine numbers.

    Question: Can I remove the engine and just replace the lh case and put back into the bike ?, does the rh case have the number or corresponding numbers stamped ?, are they matched pairs ?.

    ( the BSA I have just done has matching cases, apparently you need both left and right hand otherwise there will be additional oil leaks, you know, additional to all the normal oil leaks. :D ).

    Thanks in advance.
  2. DogT


    Jan 20, 2009
    I don't know if you need to match the cases, but I do know that if you use Hylomar Universal Blue Racing formula gasket dressing it works on the ungasketed crank case flanges just hunky dory (Amurican for just fine). It's a Permatex product, about $15USD here for enough for the whole bike, 1.2oz.

  3. chris plant

    chris plant

    Nov 6, 2008
    hi josh,short answer yes they are matched,they would have been machined as a pair,usually with a 3 digit nmbr,but not the left case engine nmbr,i think its on the underside of the cases
  4. hobot


    Oct 19, 2005
    I believe about any DS case can match to alien TS case, as Steve Maney sells just a DS case to mate factory TS case on for economy yet about full benefits plus a bit less mass. There are no ID serial numbers on the 750 TS cases I've seen. Can easy ask a vendor as for sure they will know, having saved many a Commando owner some expense to get it together. Hyolmar will definitely make up for gaps in seams oil tight permanently yet allow take apart w/o gluing. Thread fiber to back it up good idea too. I grantee you ain't likely as bad a mis match of case halves as Peel had with ~18" of welding repair, most next to the seam. Hylomar and thread sealed the top seam I could beat back closer than .003". Peels case were also tweak-toqued-twisted and lock together until I relieved back sides of location dowels .003-4" with sand paper and magic marker. Empty cases were a terror to get apart with 1/8" gap remaining to mate fully before I realized oh oh, don't want to face what initial parting took again. Main deal is crank and cam shafts center align and no excessive side slack.
  5. RennieK


    Nov 20, 2008
    Here you go... a picture is worth a thousand words.

  6. stockie1


    Jul 5, 2010
    Josh, is there something damaged on the original RH case. A god aloy welder and machinist should be able to put it right, then yo have the whole "shebang" aussie for everything! back together like it should be. Then you have a set of 71 cases that you can save or help someone else out with.
    Once you get her pulled down the timing side case comes away from the crank first, then typically the drive side need to be assisted to part with the crank. Also it would be opportune to reinstall super blend bearings if they are not alrready there.

    Cheers Richard
  7. dave M

    dave M

    Oct 19, 2005
    The issue is not where the cases meet at their edge, but that the bearing holes for the crankshaft main bearings are
    line-bored as a pair. You might get away with it but at the very least you should try to have them checked for concentricity by someone who knows what they are doing.
  8. RoadScholar

    RoadScholar VIP MEMBER

    Dec 28, 2008
    +1 for dave M
  9. dave M

    dave M

    Oct 19, 2005
    You sir, are clearly a scholar and a gentleman.
  10. rond944


    Nov 4, 2008
    You might want to have them checked even if they are matched . Leo Goff had to
    offset-bore and bush the DS case on my MK3 to get the cam bores to line up
    correctly :(
  11. RennieK


    Nov 20, 2008
    +2 for Dave!
  12. lcrken

    lcrken VIP MEMBER

    Mar 15, 2009
    Steve Maney didn't sell his heavy duty drive side case by itself. He fit it to a timing side case supplied by the customer. Maybe he has changed policy, and will sell just the half now, but I doubt it.

    Years ago I tried fitting non-matched case halves together and found the main bearing bores out of line by as much as .020". Never tried using them, so I don't know if they would work ok on a street bike or not. I wasn't willing to use them on a race bike. Might have worked, might not have. I do know of other Norton owners who have put mis-matched cases together and had them work fine.

  13. Seeley920


    Jan 6, 2009
    I have to agree with Ken. Steve needed the customers timing side and machined the drive side to match.

    I also had a new set of Mk3 cases, and the mains were .020" offset from each other (drive side was .020" higher) so I machined the bearing housings, fitted a bronze sleeve and bored it to suit the drive side. they lasted for about 8 years before finally breaking.
  14. Flo


    Aug 4, 2009
    In theory, you should be able to use unmatched pairs, as the bearing dia. should be machined with the locating dia. on the mating faces. The barrel face would probably be mismatched slightly & can be faced, after checking the distance to each bearing dia. Would be a good idea to check the barrels fit first.
    Always lap my halves together on rebuild, it is the only way to ensure no leaks.
    My matching half no's are 828 on my 850. Jealous?
  15. lcrken

    lcrken VIP MEMBER

    Mar 15, 2009
    A nice theory, but not true in reality. Several people, including me, have actually measured the bearing bore locations in mismatched cases, and they frequently are not the same. See previous posts.


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