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Primary chain event

Discussion in 'Norton Commando Motorcycles (Classic)' started by Gilesy, Apr 19, 2019.

  1. Gilesy

    Gilesy VIP MEMBER

    Joined:
    Aug 27, 2017
    chain2.jpg Chain.jpg I was out riding yesterday, fairly briskly on an open twisty road when there was a 'thump' and a judder but the bike seemed to recover. However there was a loss of power and the clutch had started to slip badly. I stopped, there was no obvious damage, however the drive chain was bar tight. The Alton starter still worked and the bike ran so I rode it to a safe place to stop and my mate came and trailered me home.
    I took off the cover and found this. What had happened was one of the set screws fixing the inner chaincase to the crank case had worked loose and had pushed the triplex chain over one row onto the clutch housing. Both chains were bar tight. I slackened off rear chain and moved the gear box right forward, I could then dismantle the Alton set up and pull the engine sprocket and the clutch hub. You can see by the damage to the inner case how far forward the clutch had moved, the force must have pulled the gearbox forward on the drive side, hence the tight rear chain. Amazingly nothing is obviously bent or broken. My question is should I put all back together and press on or what? Has this chain 'jumping' event happened to anyone else? The Alton starter has no bearing on this apart from the set screw, my fault for forgetting the Loctite.
    Cheers
     
  2. Danno

    Danno

    Joined:
    Feb 7, 2010
    What does the primary chain look like?
    <---That had a bolt fall out of the Mk III hydraulic chain adjuster and boogered one of the sideplates on the chain, so I replaced it. The MkIII gearbox is fixed in place, so no other issues.
     
  3. Gilesy

    Gilesy VIP MEMBER

    Joined:
    Aug 27, 2017
    Chain looks fine, no obvious damaged.
     
  4. Fast Eddie

    Fast Eddie VIP MEMBER

    Joined:
    Oct 4, 2013
    I don’t think the chain case screw ‘pushed’ your chain over. It looks to me like the screw got in between the chain and sprocket, this would have put huge strain on everything as the chain got pulled super tight, then when the screw got spat out, the chain fell over onto the other sprocket teeth.

    You really should check the crank and gearbox mainshafts aren’t bent. You must have strained both. The Crank primary shaft to crank cheek is a known weak point anyways.

    So long as you’re not racing, all of the above is probably gonna be fine. Personally, I would replace the primary chain. When a primary chain lets go it wreaks havoc and you don’t know how much you've weakened yours already. Just not worth the risk IMHO.
     
  5. ashman

    ashman

    Joined:
    Jul 11, 2010
    Give everything a good clean and inspection, if all OK then put it back together with loctite this time and let it set over night, give all chains a good clean and make sure every link is good and you should be all good to go.

    Ashley
     
  6. 1up3down

    1up3down

    Joined:
    Jan 12, 2011
    Fast Eddie:

    Personally, I would replace the primary chain.

    yes
     
    marshg246 and JimC like this.
  7. RoadScholar

    RoadScholar VIP MEMBER

    Joined:
    Dec 28, 2008
    Chain and sprockets, if the rest of the band is able to strike up a tune. It doesn't take much, however, to bend the mainshaft (or layshaft), at least check it and the crank for run-out. If you can easily remove the clutch rod, and if it rolls true on a proven flat surface, that's a good sign, but doesn't mean you are out of the woods, if the clutch rod wants to lay flat and not rotate.....The fact that you could push it onto a trailer or bed of a truck is a positive sign.

    If the clutch moved forward that far, I'd wager that the mainshaft has taken a measurable set and it would be prudent to check the transmission case for cracks...

    Sorry for you fella, what a mess. I can almost feel your pain and sincerely hope I'm dead wrong; I also hope you find a solution on the surgical deck, not the answers in the coroners office.

    Best.
     
    JimC likes this.
  8. illf8ed

    illf8ed

    Joined:
    Dec 30, 2003
    Look at the chain closely. Those look like chain roller pieces in the case. I have experience with this failure. At quick view the chain looks OK. Like Jim said best to replace it and also look inside the clutch for more broken parts.
     
    JimC likes this.
  9. Torontonian

    Torontonian

    Joined:
    Dec 28, 2009
    Yes those sure look like chain rollers so replace the chain.
     
  10. ashman

    ashman

    Joined:
    Jul 11, 2010
    Be a good time to replace the chain with a duplex chain from the chain man.

    Ashley
     
    kommando likes this.
  11. Gilesy

    Gilesy VIP MEMBER

    Joined:
    Aug 27, 2017
    Thanks for all your replies. I think fast Eddie is right in that the screw got caught between chain and sprocket, the force of which kicked it over a row and pulled the gearbox forward . The swarf is all aluminium, I've run a magnet through it. Even so replacing the chain seems like the safe option. What makes the duplex chain better? Can you get them from 'The chainman' even though I don't think it's Andy anymore. The mainshaft spins with no play in the bearing and the push rod works OK. I rolled it on a piece of engineers glass and it ran true. The other puzzle is that the other two screws securing the inner case were also loose. I realise I didn't use Loctite because they came with spring washers. It would have been a very bad day to not tighten all three. Perhaps best to contact Monsieur Alton starter motor.
    Cheers
     
  12. kommando

    kommando

    Joined:
    May 7, 2005
    Its made by Iwis and originally designed for Mercedes timing chains and their requirement to last, it has the largest pin size allowed within the confines of the size parameters and the best materials, so making the chain, which is a series of bushes held together by steel links, both long lasting and strong. First used by Andy as a replacement for the Triplex primary chains for Laverda 1000 triples when they stopped being available, these pump out more HP and Torque than a Commando.
     
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  13. ashman

    ashman

    Joined:
    Jul 11, 2010
    The triplex chains today are not as good quality as days gone by and Andy the chain man was selling the duplex chains of better quality, he has retired but not sure if its his son or someone else took over the business, I replaced my triplex chain with a new one that I had its a Renols chain but not as good as the orginal chain and soon will be replacing it with the duplex chain from the new chain man, there has been good reports about running the duplex chain with better quality and smoother running.

    Ashley
     
  14. jimbo

    jimbo VIP MEMBER

    Joined:
    Sep 25, 2004
    Are these the screws that came out? Is there room for hex heads and lock wire?


    alton inner cover.jpg
     
  15. jbruney

    jbruney

    Joined:
    Jan 5, 2019
    You guys make me feel bad. the only time I see a dirty Commando is when it has connecting rods hanging from a hole in the crankcase...Mine is just a dirty backstreet tramp in comparison to these. Even the used oil looks waxed...
    I know I've used the 'word' before, but since you've got it down & it's suffered a known considerable shock this is the time to pull out the old magnaflux kit. There's nothing like the assurance of knowing that unseen fractures are,or are not there. You can get water based which cleans up easier, though the regular is better IMO. It can and will show any cracks in the affected areas. Just $.02 from the gallery.
     
  16. RoadScholar

    RoadScholar VIP MEMBER

    Joined:
    Dec 28, 2008
    That the clutch push rod rolls and appears true is good news. Have you, or are you planning to dial indicate the mainshaft and crankshaft?

    I recommend taking a hard look at the teeth on the engine sprocket and clutch basket; if you see any cracked or seriously bent teeth I'd encourage you to consider replacement. I would think that the sprocket(s) that picked up the passenger fastener has got to show some damage, the only question here, in my mind is whether or not the damage can be repaired, which may (should) be a moot point.

    Because.

    Given what the chain went through I'm surprised that there is any talk of re-using it; clean it up, chrome it up, put a belt buckle in it and sell it to a 1%er. Anyway. If the sprockets are original proper protocol would be to replace sprockets and chain as a set. Conceivably Alton included both, don't know, but if so, and they aren't seriously damaged, they may be worth rolling the dice for.

    I'd like to see pictures of the sprockets and the chain.

    Best
     
  17. jbruney

    jbruney

    Joined:
    Jan 5, 2019
    For myself I'd toss the chain & engine sprocket, give serious consideration to the clutch basket if damaged. The shafts do indeed deserve an indicator, as the trans case & crankcase should have thorough inspection for cracks. If the bike were mine I would do the magaflux dye check on those two areas surrounding the shaft penetrations because if any are indicated they likely shall grow through time/further use. Probably won't find any, but I tend to lean to the safe side on failures like this.
     
  18. ashman

    ashman

    Joined:
    Jul 11, 2010
    I think you are all going overboard now with talk of cracks sprocket bent shafts etc etc, do a visual inspection after a good clean up, yes replace the chain but worring about anything else I am sure would have servived without damage, put it back together with loctite etc and take it out if there any major damage you will know after riding it but I recond it will be fine, remember its a street bike and if you know your own bike you will know if something is wrong. I have had things fail before on my Norton over the 43 years of ownership some been a easy fix others a bit more thinking or replacing the failed parts, one of my major failures was my rear brake drum and sprocket where the circlip casting mount broke and only about 30mm left and the circlip fell out, ordered a new drum and while waiting for it to come from RGM I put the drum up on a lathe and machined the circlip mount deeper and put a bigger circlip in, well after 7 years now its still working and the new drum is still sitting under my workbench.
    It can be very stressfull over worring about what might happen and if it was my bike it be back together now riding it and I would know if its not right, but I do know my own bike.

    Ashley
     
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  19. franko

    franko VIP MEMBER

    Joined:
    Dec 29, 2013
  20. Reggie

    Reggie

    Joined:
    Jul 24, 2006
    This is who now runs Andy the chain man's business.

    https://the-chain-man.co.uk/

    These are his contact details.

    "Call us today on 07564870313 or Email us at jason@the-chain-man.co.uk"
     
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