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Gearbox mainshaft bearing upgrade? (2017)

Discussion in 'Norton Commando Motorcycles (Classic)' started by fiatfan, Aug 20, 2017.

  1. fiatfan

    fiatfan VIP MEMBER

    Joined:
    Aug 9, 2015
    There´s loads of threads on the layshaft bearing upgrade here, but is there an upgrade for the mainshaft drive side bearing as well? Or is the old ball bearing type good enough?
    Just realized it´s called sleeve gear bearing....To quote the great Danish comedian Viktor Borge; it´s not my language, I´m just trying to use it..... :D
    Tommy
     
  2. kommando

    kommando

    Joined:
    May 7, 2005
    No upgrade I am aware of, it's a odd size which limits volumes so less scope, there may be sealed versions around but not looked as never had an issue with it unlike the layshaft which did fail.
     
  3. NortonMKIIA850

    NortonMKIIA850

    Joined:
    Jul 20, 2017
    When I refurbished my gearbox this summer, someone on the UK NOC forum helpfully suggested getting a sealed bearing and removing one seal, on the side that would face into the gearbox - a bearing with one seal is available for this purpose from AN: https://andover-norton.co.uk/en/shop-details/18011 – AN call the seal a 'shield', but I believe it's the same thing. I went for this, as gearbox oil residue on the inner diameter of the inner race of the old bearing contained rust. Whether fitting a bearing with a seal/shield on its outer face could be considered an upgrade, or would make any difference to my issue, I don't know, but it seemed like a good idea and couldn't hurt. HTH
     
  4. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    'Sealed' (RS/2RS) and 'shielded' (Z/ZZ) bearings are not the same.

    http://www.ebay.co.uk/gds/Ball-Bearing- ... 758/g.html
    http://www.astbearings.com/bearing-closures.html
     
  5. NortonMKIIA850

    NortonMKIIA850

    Joined:
    Jul 20, 2017
    Interesting – so the bearing I fitted is unlikely to make any difference to what I found at all! Oh well – why might AN be selling that bearing, then? I can't imagine any flying debris hitting that shield – er, fingers crossed!
     
  6. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    As far as performance or reliability is concerned I don't think it makes any difference.......


    I believe the shield on the outside of the bearing was intended to reduce the amount of oil thrown at the sleeve gear oil seal. According to Mick Hemmings in his gearbox rebuild video, he says the early bearings were the shielded type but that the shield isn't really necessary.
     
  7. no750

    no750

    Joined:
    Apr 7, 2016
    2 years ago i aquiered a "not runner" 750. not actually a good buy. also the gearbox main bearing seat was damaged - lots of free space to the bearing due to a gear wheel failiure. the guy doing some mashining on the motor said, he can reinforce the case by deposition welding and rebore the main bearing seat in order to use a needle bearing, leaving more meat between the bearings.

    this is what i am ended up with. the gearbox is working fine for the last 1200 miles, hopefully i can tell you in 10 years this was a fabulous approach.
     
  8. Torontonian

    Torontonian

    Joined:
    Dec 28, 2009
    Iv'e got a MK 111 gearbox in my pile of stuff that has a roller bearing fitted in place of the large mainshaft ball type. It's outer diameter is less than the shell hole size , so the machinist made up a sleeve to take up the difference and fit it. Worked well when I last ran it 30 years ago. It also runs the roller layshaft bearing . Overkill maybe but I had extra cash 30 yrs. back. Hope that helps. :)
     
  9. NortonMKIIA850

    NortonMKIIA850

    Joined:
    Jul 20, 2017
    Ah ok – thanks again – well, I'm a fan of anything that helps keep oil where it should be!
     
  10. fiatfan

    fiatfan VIP MEMBER

    Joined:
    Aug 9, 2015
    Thanks, great input as usual. So I´ll just buy a good quality bearing then, hope my usual bearing supplier can find one, even if they are an odd size. Don´t Think that´ll be a problem. If so I´ll take one from RGM or the like. I will have to find a good compound to lock the bearing both on the sleeve and in the housing. There were signes showing that the bearing had turned on both in and outside.
    Tommy
     
  11. Torontonian

    Torontonian

    Joined:
    Dec 28, 2009
    Whatever large bearing you choose I would make sure it does not rock about it it's shell bore. I hope this is not a concern. Heat and cold.
     
  12. fiatfan

    fiatfan VIP MEMBER

    Joined:
    Aug 9, 2015
    I hope so too! :wink: I´ll try find the best locking compound for the job, as I wrote there was small signs that it had turned both in the house and on the sleeve. I´ll clean the surfaces and measure the new bearing, the sleeve and the bore in the shell, hope it´s enough with locking compound.
    Tommy
     
  13. oldmikew

    oldmikew

    Joined:
    Jul 25, 2015
    the factory used both dot 2 and dot 3 clearance bearings.. there is quite a lot of play with a dot 3 -just think about those bronze bushes the main shaft can wiggle in .. could not get dot 2 when i replaced mine but it turns out a lot of 850s where fitted with these and made in japan.. and they failed much to the amusement of we xenophobic Brits. Truth is just pull the primary outer start the engine and blip the throttle. the amount of flex on the shaft is terrifying

    no wonder there was a problem under racing conditions and recourse to outrigger bearings- the bodge for we the punters was dot three ,lets the shaft flex
    presumably. if there is one thing that does not impress me about the commando... this is it. Good tip when replacing them is to put soap on the alloy casing when it goes brown under your torch flame-you are approaching the temp you want... i made up a jig out of thick dural which bolts on to shell so as to ensure bearing starts straight when replacing them
     
  14. Madnorton

    Madnorton VIP MEMBER

    Joined:
    Jun 9, 2008
    In the past many of the sleeve gear bearings were ground, this was done as the correct size was not available for sometime. The availability of the correct size bearing is now far better, as for a roller, it maybe possible to get one that size. I know of one manufacturer that supplies alternative roller and needle bearings as direct replacement for most of the standard sizes.

    Bearing fit will work, but it can cause the bearing to close up, but considering the temps involved when in use, I would not consider it an issue provided it is checked when fitting of the bearing and the sleeve gear is complete.
     
  15. jimbo

    jimbo VIP MEMBER

    Joined:
    Sep 25, 2004
    If you use a roller type bearing on the sleeve gear what locates it? Anybody know the special correct OD dimension of the SG bearing?
     
  16. jimbo

    jimbo VIP MEMBER

    Joined:
    Sep 25, 2004

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