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Why we call it "inspection"...

Discussion in 'Norton Commando Motorcycles (Classic)' started by concours, Jan 8, 2018.

  1. concours

    concours VIP MEMBER

    Joined:
    Dec 29, 2011
    Very good. It's 50% obscured. I'll relieve the new shell to suit. Other rod is spot on.
     
    MikeG likes this.
  2. MikeG

    MikeG

    Joined:
    May 31, 2012
    Kind of disconcerting that its off that much.
     
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  3. hobot

    hobot

    Joined:
    Oct 19, 2005
    Maybe too tight a clearance C1 or C2 bearing fitted instead of C3? If case bores still need serious heat to release/replace outer races from cases then lucked out big time. The end of the flake damage distinctly ends at outter edge of less worn inner race rim. Hm. Cranskhaft combustion heat and loads would heat bearing from cheek outward most with coolest part deepest in case from oil flow and case heat conduction. Too tight installed clearances with rollers getting hotter at one end than the other, taking on a cone shape may account for the damage size and shape. Rare but case bores might be tad tight another checking consideration to avoid another flaky image.

    Ever keep track of wrenching worrying vs relaxed riding hours?
     
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  4. concours

    concours VIP MEMBER

    Joined:
    Dec 29, 2011
    That engine owes me nothing... 31,000 miles of spirited great riding times.
    I'll be checking everything, to rule out a repeat performance.
     
  5. hobot

    hobot

    Joined:
    Oct 19, 2005
    hehe that's the spirit fix em up use em up till ya can't. Such obsolete cycles just shouldn't keep exciting us easy thrill seekers so much but sure glad they do. Ok inspired enough to go shopping again, thanx I think.
     
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  6. Torontonian

    Torontonian

    Joined:
    Dec 28, 2009
    Looks obstructed from here, so be it.
     
    concours likes this.
  7. concours

    concours VIP MEMBER

    Joined:
    Dec 29, 2011
    It is obstructed. I think my choice of word was poor...
     
  8. bill

    bill

    Joined:
    Jun 1, 2003
    not a problem. you can even totally block it by swapping the top and bottom shells with NO bad effects and some do it deliberately.

     
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  9. Fast Eddie

    Fast Eddie VIP MEMBER

    Joined:
    Oct 4, 2013
    If you buy Carrillo rods etc, they do not come with oil holes as standard. So many a good engine has indeed been built without these holes, with no ill effect.

    If you think about it, where else can the oil go? Without the holes, more will simply exit out of the sides of the shells and result in ‘splash’. Thus essentially doing the same thing as the hols would have. Plus, the added pressure build up caused by not having holes, must be beneficial to the big end journals.
     
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  10. oldmikew

    oldmikew

    Joined:
    Jul 25, 2015
    What is the actual bearing ? is it dot 2 or 3 . The factory did turn to Japanese suppliers at some point who seemed to prefer tighter clearences For instance the factory fitted sleeve gear bearings (made in Japan) were dot 2 and they failed...But there is another possible issue here, there is no positive crank location with double roller bearings so maybe there was excessive endfloat
     
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  11. oldmikew

    oldmikew

    Joined:
    Jul 25, 2015
    The seriously disconcerting thing about oem rods is that the factory stopped balancing them one against the other, engineering by accountants who thought that because the rider would not feel vibration thanks to the isolastics there was no need
     
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  12. MikeG

    MikeG

    Joined:
    May 31, 2012
    Engineering by accounting...sounds much like my place of employment :( It's Ok to sit on a paint shaker as long as the seat and bars don't move, right? :rolleyes:
     
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  13. Danno

    Danno

    Joined:
    Feb 7, 2010
    More like lack of investment in tooling and modern design. And not taking the competition seriously. Wonder how many of us are rolling on cases align-bored with a chunk of 2x4 jammed between the arbor and the upright?
     
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  14. oldmikew

    oldmikew

    Joined:
    Jul 25, 2015
    the late John Hudson who worked at Bracebridge street said that the machining of the crank cases was so accurate that they were treated as being interchangable..There is actually an amazing website called workingatamc.. What astonised me was how uptodate the tooling in use at Plumstead actually was.. The engineering by accountants came later and was simply penny pinching. Do not know what year it kicked in , but if i had a Combat engine certainly I would want to ensure the rods had been balanced. 72 saw the most number of revisions to the original engine..
     
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  15. comnoz

    comnoz VIP MEMBER

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    Dec 10, 2008
    What are you using for ignition.
    Too much advance will do that.
     
  16. MikeG

    MikeG

    Joined:
    May 31, 2012
    Not Norton, but when I replaced the timing side bush on my BSA A10 I mounted the drive side on the mill table, indicated the main bearing hole to within +/_ .0001 and then bolted the timing side case on. It was almost .008 out of alignment. Ended up fabricating a much undersized bushing and boring it to suit. These were matched number cases, unknown number of miles, but the holes were still round, just not aligned.
     
  17. MikeG

    MikeG

    Joined:
    May 31, 2012
    Might that be the effects of pre-ignition then Jim? Excessive combustion chamber pressure putting a much higher load on that one spot of crank rotation?
     
  18. concours

    concours VIP MEMBER

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    Dec 29, 2011
    Boyer, 1980 mfg. date. I strobe timed it, it felt numb, Dyno dave heard me ride across his yard, "sounds retarded"...
    "I know"
    So, I bumped it up a couple degress until it pulled and sounded good, yet no audible pinging.
    The half dozen times I got shit gas sold as Premium, it would audibly protest 1/2 to 1 mile from the pump. I'd try to go easy, not ask much of it, free rev rather than lug, and dilute with (another attempt) at good fuel after 30-50 miles.
    There were heavy combustion chamber deposits, so compression could have been a bit up.
     
    Last edited: Jan 10, 2018
  19. comnoz

    comnoz VIP MEMBER

    Joined:
    Dec 10, 2008

    That is the only reason I do not like the old analogue Boyer.
    With the lazy advance curve it has you have to advance the timing quite a bit over the recommendation to get it to pull strong through the midrange.
    Then you end up with 36 degrees at 5000 rpm and that is too much. Even without audible pinging the bearing load would have a spike that probably shortened it's life. Jim
     
  20. hobot

    hobot

    Joined:
    Oct 19, 2005
    Huh, too adv spark would resist crank journals rise, which would bow mid crank down so ends supported in bearings would tend to 'piviot' there and pry upward. It was sloppy point adv mech in early Combats that vastly accelerated their crank bearing fails. So real 1st cause may of been trying to nurse a failing battery too long.
     

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