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Identify Main bearings

Discussion in 'Norton Commando Motorcycles (Classic)' started by brian4.2, Mar 13, 2018.

  1. brian4.2

    brian4.2 VIP MEMBER

    Joined:
    Jun 1, 2016
    IMG_2694.jpg IMG_2695.jpg Hi All. I have split the cases on my "combat" motor and I found 2 identical bearings. I thought the combat motors had 1 Superblend and one other type? The PO said he doesn't think the cases were ever split. Another thing that seems to be missing is the copper tab washer that sits behind the beveled washer on the cam timing side.

    Can someone identify these bearings tell me if a like pair was ever in the combat from the factory?

    Also is there a way to identify the "combat" cam from the standard
     
  2. kommando

    kommando

    Joined:
    May 7, 2005
    The Combat like all 72's came with 2 identical rollers, the Superblend rollers were a late 72 model fitment at the factory and as service replacements and again fitted as pairs. You have to post the markings on the bearings to identify them which may need removal to see, early Superblends have hand etched number added, later ones are all stamped. Earlier engines had one roller and one ball which may be where the confusion comes from. To identify Measure the cam lobes peak diameter and take away the base diameter to give you the lifts and then compare to the figures in the manual.
     
    Last edited: Mar 14, 2018
  3. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    The original roller bearings would normally have been (brass-cage?) R&M MRJA30 with double lipped inner, and single lipped outer races (or 'NF' type) with the rollers captive on the inner race (below) so those steel cage 'NJ' type probably aren't the original bearings.

    [​IMG]

    [​IMG]
     
  4. bill

    bill

    Joined:
    Jun 1, 2003
    it has been split open as evedance of the flanged cam bush in the timing side case. with that bush the troublesome tab washer is NOT used.
     
    brian4.2 likes this.
  5. dynodave

    dynodave

    Joined:
    May 28, 2003
    Its obvious the engine has been split and "worked" over by a hack. IMO
    On the table behind me I have almost every ball and roller bearing norton heavy twin used...
    The bearings shown are NOT FACTORY..and..poor substitution IMO
    The bearing shown have 11 rollers and as LAB stated are steel cage so are NJ306 but probably not FAG and NOT 12 roller NJ306E(heavy duty). Fag NJ306 11 roller DOES have a brass cage.
    All that aside the early fag NJ603E are difficult ( for me, so far) to verify they are C3 clearance. Todays FAG and NTN are marked C3 on the bearing.
     
    Last edited: Mar 14, 2018
  6. APRRSV

    APRRSV VIP MEMBER

    Joined:
    Jun 26, 2016
    Hi Dave and all,
    I note that RGM, for one, sells both "standard" and C3 clearance superblends. Is the C3 clearance critical?

    Thanks,
    Ed
     
  7. dynodave

    dynodave

    Joined:
    May 28, 2003
    Depends how lucky you feel and are you willing to rebuild you engine again if the problem comes to haunt you.
    I have assembled 3 engines with std clearance bearings. Oven heat the cases, drop in the new fag bearings (not marked for C3 clearance),
    put crank in, bolt together to do the end play test. Seems to spin OK and let cool down.
    Now cool (room temperature)... the cranks do NOT slide in and out for end play unless you put a crow bar or fat screwdriver and force the movement by pushing on the crank cheek. They turn but seem tight. This has been in both early engines 650ss/manxman and later commando with the resized crank. They were all redone in C3.
    Once this was going to be done to a 68 commando with bearings from a LONG TIME north american brit part dealer who (claimed) he was unaware of the C3 issue. What kind of tight fit do you have when the engine is started cold??? They were returned and we could not wait and bought the NTN C3 bearings.
    Less money and they worked great. Then I bought 2 NTN sets for myself. About $60 ea IIRC

    Remember one thing...the whole point is that bearings are engineering/sized for steel or iron housings and the extra shrink fit for non standard aluminum housings call for C3 clearance. I once left Watertown New York, 10 at night at 5 above zero "f" on my 70 roadster. Not a good trip! called it off after about 75 miles. The mains would have been super tight under those conditions and you might have results like concours had!!! see his pix

    I have a set of std clearance I will NEVER use in a norton I build.
    for sale cheap$$ car or truck rear axle bearings???
     
    Last edited: Mar 14, 2018
  8. APRRSV

    APRRSV VIP MEMBER

    Joined:
    Jun 26, 2016
    Thanks Dave. You have convinced me. I have three pairs. One pair is not marked C3. Brian, do you want a cheap pair of superblends? :)
     
  9. brian4.2

    brian4.2 VIP MEMBER

    Joined:
    Jun 1, 2016
    Thanks Bill, I thought that might be the case with the flanged bushing. Is that flanged bushing a common fix?

    Thanks Dave, Great stuff. Going forward I can correct the bodges. bearing is an
    SKF (sweden ) NJ306




    I will surely get the NTN or FAG C3 clearance Bearings.

    Thanks Ed, I think not. Do you have a breather solution?

    IMG_2696.jpg
     

    Attached Files:

    Last edited: Mar 14, 2018
  10. Mr. Rick

    Mr. Rick VIP MEMBER

    Joined:
    Feb 6, 2009
    Does a rating of ABEC 1 indicate enough precision for our application?
    Anyone find them with a higher rating?
     
  11. dynodave

    dynodave

    Joined:
    May 28, 2003
    Brian
    I partially take back the hack bit....the flanged 850 cam bearing is a very good/super highly recommended upgrade. Original combat style is super bad karma.

    Under the thermal expansion hell these bearings live under, I would think the C3 tolerance takes care of it mostly and going up from ABEC1 will only send the price through the roof for not really dealing with the expansion problem.
    A standard clearance (non C3) to ABEC 7 would likely still be to tight IMO
     
    Last edited: Mar 14, 2018
  12. MFB

    MFB VIP MEMBER

    Joined:
    Mar 29, 2012
    [QUOTE="dynodave, Oven heat the cases, drop in the new fag bearings (not marked for C3 clearance),
    put crank in, bolt together to do the end play test. Seems to spin OK and let cool down.
    Now cool (room temperature)... the cranks do NOT slide in and out for end play unless you put a crow bar or fat screwdriver and force the movement by pushing on the crank cheek. They turn but seem tight.[/QUOTE]

    I had the same scenario when upgrading my 1970 bike a few years ago with parts sourced from Norvil. Bearings were FAG "superblend", but Norvil prefer to supply standard clearance.
    After experiencing the problem described by Dave, I bought FAG NJ306E C3 bearings from a local Australian supplier. The ones supplied by Norvil wasted my time and money.