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Another TIGHT engine sprocket.

Discussion in 'Norton Commando Motorcycles (Classic)' started by 998cc, Mar 30, 2019.

  1. 998cc

    998cc "Cheap" is rarely the least expensive. VIP MEMBER

    Joined:
    Oct 1, 2018
    I decided to go into the gearbox and change out the layshaft bearing today. All went like clockwork until I got into the primary and finally to the engine sprocket. I've never seen anything this tight on a shaft. The puller is pretty stout; it is US made and was my dad's for about 50 years. As suggested in another thread, I tried heating the sprocket (carefully to avoid heating anything else) until it produced a bit of smoke. No joy at all. The other problem is the puller wants to go out of line with the crankshaft when under stress. Also tried a new puller from the auto parts store which is stout as well. Same result.

    Cussin' the designer isn't getting me anywhere--;) Anyone have any suggestions?

    ~998cc
     
  2. Lineslinger

    Lineslinger VIP MEMBER

    Joined:
    Feb 26, 2017
    Cubed ice or dry ice on the shaft after a long soak in penetrant.
    When you think you can’t heat the sprocket any more give it another 15 seconds and then give the shaft a good shock with a hammer. Sprocket next.
    It takes serious shock to break loose serious binding.
     
  3. Nortoniggy

    Nortoniggy

    Joined:
    Nov 17, 2010
    They certainly can be tough to remove. I use a drift to shock the sprocket that is a very stout old tyre lever with the end ground so that it will fit between the rows of teeth on the sprocket so that the impact gets transmitted through the sprocket. First tighten the correct extractor as much as you can then give the sprocket a good whack.

    Ian
     
  4. baz

    baz VIP MEMBER

    Joined:
    May 26, 2010
    I take it you are using a 3 legged puller or suchlike as it belonged to your dad?
    You need to buy or make a puller that screws into the engine sprocket then give it some welly
    Give the head of the extractor bolt a clout
    If that doesn't work apply heat in one spot only to the sprocket and give it a clout
    Hopefully that will get it off
    Cheers
     
    concours likes this.
  5. baz

    baz VIP MEMBER

    Joined:
    May 26, 2010
    And whilst you are doing it stay calm and think what a great job those blokes made
    Machining those tapers so accurately that it's still so tight
    Cheers
     
    998cc likes this.
  6. cyclegeezer

    cyclegeezer

    Joined:
    Jul 15, 2010
    Leave it under tension and walk away. Overnight if necessary. The mechanical gnomes are shy and won't work if you are watching.
     
  7. 998cc

    998cc "Cheap" is rarely the least expensive. VIP MEMBER

    Joined:
    Oct 1, 2018
    Good morning C.G.

    I thought the same and left it under tension all night. Still firmly in place this morning. Being Saturday night, the gnomes were likely at the pub. :cool:
    Below is a photo of the puller in place and under tension; it is a combo two or three way puller. The nose of either puller would not mesh properly with the end of the crankshaft. This is why the crankshaft nut is installed; it is holding a sleeve in place that better transfers the puller's pressure/tension. The bolts are grade 8.

    The glob of blue silicone on the stator cable shows the primary has been opened before, and the chain looks new. If that is the case, the sprocket had to have been off at some point--yes?

    IMG_0275 (1024x683).jpg


    ~998cc
     
  8. 998cc

    998cc "Cheap" is rarely the least expensive. VIP MEMBER

    Joined:
    Oct 1, 2018
    Agreed, and I do appreciate the fine craftsmanship of the taper and mating surfaces. However, it seems a splined shaft/sprocket would have done just as well and would be infinitely easier to service.

    ~998cc
     
  9. 998cc

    998cc "Cheap" is rarely the least expensive. VIP MEMBER

    Joined:
    Oct 1, 2018
    SUCCESS!! Heated it up again--but more thoroughly and brass drift to the sides of the sprocket--nothing. Then one moderate tap on the end of the puller. Pop! The project continues. :D

    Thanks to all who replied. Dry ice was next.....

    ~998cc
     
  10. baz

    baz VIP MEMBER

    Joined:
    May 26, 2010
    Brilliant news
     
  11. swooshdave

    swooshdave

    Joined:
    Apr 15, 2009
    A sharp wack on the end of the shaft is sometime all it needs as was the case here.
     
    998cc likes this.
  12. Bob Z.

    Bob Z.

    Joined:
    Mar 30, 2012
    Did it release with a pop or !!POP!!.
    I've experienced the same issue and when it finally let go using the same techniques, there was a loud BANG.
     
  13. Lineslinger

    Lineslinger VIP MEMBER

    Joined:
    Feb 26, 2017
    It’s always gratifying when you win one of the Gremlin battles.
     
  14. 998cc

    998cc "Cheap" is rarely the least expensive. VIP MEMBER

    Joined:
    Oct 1, 2018
    Bob. It was just a "pop!" and the sprocket and puller fell away from the shaft. No bangs to speak of.

    Layshaft bearing was pretty tight in the case; heated the case and was still hesitant but came out without trouble using a puller. New layshaft roller bearing is installed in its place. The large output shaft bearing came out fine, but the new one is problematic going back in with the case heated. Tried freezing the bearing-no go either. Might get varied opinions here, but the gearbox case is still in the bike which does make bearing install a little more difficult. Really would rather not pull the whole box but may have too. o_Oo_O

    ~998cc
     
  15. cyclegeezer

    cyclegeezer

    Joined:
    Jul 15, 2010
    Glad it finally freed up!
     

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