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Spacer between head stock bearings

Discussion in 'Norton Commando Motorcycles (Classic)' started by olympus, Mar 9, 2019.

  1. olympus

    olympus

    Joined:
    Aug 5, 2017
    Just fitting new headstock bearings, installed the bottom bearing fully home. Inserted the spacer tube ands drove in the top bearing .... but i was expecting the spacer tube to be "nipped" between the two bearings, but it isn't??
    Is the spacer suppose to be nipped between the bearings
    If so my spacer must be worn
    So does some kind person have the overall length of the tube please

    Many thanks
     
  2. marshg246

    marshg246 VIP MEMBER

    Joined:
    Jul 12, 2015
    I've changed the bearings in many. The spacer is never long enough to do anything of value. Some will say that when the yoke is installed and tightened that the bearing inner races will be in contact with it - I've tested that theory - they are not.
     
  3. acadian

    acadian VIP MEMBER

    Joined:
    Mar 5, 2010
    Or simply convert to tapered bearings and forget about the spacer all together
     
  4. marshg246

    marshg246 VIP MEMBER

    Joined:
    Jul 12, 2015
    Every time I do it I think the same thing but afterwards don't think to lookup what tapered bearings would fit for the next time. Do you happen to have a bearing number for them?
     
  5. Holmeslice

    Holmeslice VIP MEMBER

    Joined:
    Sep 27, 2009
    The spacer should be a slight interference with the inner race of your bearings. I believe (on a Saturday, from home) the length of the inner spacer is 5.020", and the bearing shoulders *should* be 5" apart. I can measure spacers on Monday when in the shop if necessary. But if you're trying to fit sealed bearings to an older frame where loose balls were initially fit, that space is much longer and the stock inner spacer won't work. If this is the case you either fab your own inner spacer, or fit tapered rollers as mentioned.
     
  6. Mike B

    Mike B

    Joined:
    Oct 16, 2015
    Taper bearing # 30205
    Mike B
     
  7. marshg246

    marshg246 VIP MEMBER

    Joined:
    Jul 12, 2015
    Thanks! Ordered - will use on the next one.
     
  8. olympus

    olympus

    Joined:
    Aug 5, 2017
    Now you mention it i believe the frame isn't original so this is probably the case, sealed bearing were removed. but the person who put them in probably didn't bother to check
     
    Last edited: Mar 9, 2019
  9. olympus

    olympus

    Joined:
    Aug 5, 2017
    This is what it'll do also... Thanks guys
     
  10. acadian

    acadian VIP MEMBER

    Joined:
    Mar 5, 2010
    Nachi Tapered Roller Bearings Japan - 25x52x16.25

    https://www.bearingscanada.com/prod...MImIOQ-uf14AIVy7jACh0PHQ-oEAYYASABEgLDIPD_BwE

    Installed, the uppers sit about 1/16" proud of the headstock, but I'm running aftermarket yokes with adjuster nuts under the top yoke so I didn't find this problematic
     
  11. marshg246

    marshg246 VIP MEMBER

    Joined:
    Jul 12, 2015
    I just measured a spacer that I'm certain is OEM from a 72: 5.050" and another I'm certain is OEM from a 74: 5.062". Both had sealed bearings that I'm pretty sure were were OEM and the spacers were loose before removing the bearings. In the case of the 72, it was in an outdoor scrap heap from 1976, untouched all that time. I bought a 72 that was in a pole barn and the junk from the same guy. When I rebuild the pole barn 72, I compared the spacer it had to the others and used it because it was the longest at 5.065.

    Junk Heap.JPG
     
  12. olympus

    olympus

    Joined:
    Aug 5, 2017
    Many thanks for the spacer dimension, I'll speak with our machine shop and get one turned down.
    Now for the guys who have installed taper roller bearings...
    1. did you still lnstall the spacer shim under the top dirt shield?
    2. And with regard to the lower bearing, what form of sealing did you use as there is no lower seal "O" ring or dust shield so the bearing grease could easily get contaminated & some product will inevitably come out?
     
  13. Servodyne

    Servodyne

    Joined:
    Aug 24, 2013
    I've just replaced the steering head bearings on my newly bought Commando and the spacer tube was loose when I took the old bearings out. This explained why the races had become so heavily indented, that the steering self centred in the indents and was ready to tank slap at the slightest provocation. Although this made for a very engaging ride I thought this had to be sorted out before it sorted me out.
    When I tapped in the new bottom bearing in to what I thought was 'home' the spacer tube didn't extend past the recess where the top bearing sits so I would end up in exactly the same situation as I was before. If I'd just clamped the whole assembly up with the top yoke there would have been undue pre-load applied to the bearings causing them to fail again very rapidly. Using a drift tube I'd made from the old bearing outer race I decided to give the new bottom bearing a good smack with a hammer to make doubly sure it was fully home. It took a bit of force but this time it was fully seated and now the spacer tube extended a good few thou past the top bearing recess. Installing the top bearing so that it just 'nipped' the spacer tube, the top yoke now clamped on and fully assembled the Commando now handles like a featherbed. If I was doing this job again, I would make doubly sure that the bottom recess was meticulously clean and free of old paint or powder coating before attempting to install the bottom bearing.
    With regard to fitting taper roller bearings, I don't see how this could possibly work with the standard yokes, as the Commando yokes don't have any means of adjusting the bearing pre-load between the yokes.
     
  14. concours

    concours VIP MEMBER

    Joined:
    Dec 29, 2011
    I got a 7/8-14 spieth nut to adjust mine, finer than the tab washer.
    https://www.spieth-maschinenelemente.de/en/products/locknuts/msr/
     
  15. Servodyne

    Servodyne

    Joined:
    Aug 24, 2013
    Aye, that would lock it in place. That's a nice bit of kit. I'd like to use one on the shock absorber on my A10 crankshaft?
     
  16. dynodave

    dynodave

    Joined:
    May 28, 2003
    frames up to 70 (rear cross bar) were for the loose balls and the machined bearing recess' are avg 5.25" apart


    71(pin side stand) + up were for ball bearing and were machined to avg 5.0"spacing apart and lower bearing and is 1/8" up inside the neck tube. spacer tube avg 5"+ a little.
     
  17. baz

    baz VIP MEMBER

    Joined:
    May 26, 2010
    Out of interest why would you want one of these on a BSA crankshaft shock absorber ?
     
  18. olympus

    olympus

    Joined:
    Aug 5, 2017
    I'm going to have a spacer turned up... i have established the spacer on mind needs to be 5.225" this is because the frame is a lot earlier that the rest of the bike and originally had loose ball setup & I'm not happy at this point in putting in tapper roller bearings as sealing the lower race is unclear
     
  19. Servodyne

    Servodyne

    Joined:
    Aug 24, 2013
    There's no effective locking on the standard crankshaft nut securing this and they have a habit of coming loose. I've fitted a SRM nut which has a hexagon drive so I can apply a good bit of welly to tighten it but you never know even with loctite.
     
  20. Servodyne

    Servodyne

    Joined:
    Aug 24, 2013
    I used to fit taper roller bearings in my featherbed Dominators in my youth many years ago but found the biggest enemy was always corrosion due to lack of sealing
    and not wear. I discovered the Commando set up with deep groove sealed ball bearings and have never looked back after decades of use and many many miles.
     

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