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8V Failure info.

Discussion in 'CARC' started by pete roper, Jan 18, 2009.

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  1. pete roper

    pete roper GT Godfather!

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    Got a cam & tappets that's failed.

    File will mark the cam.

    Off to the Mint this week.

    Pete
     
  2. Steve uk

    Steve uk Tuned and Synch'ed

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    Re:Got an 8V cam......

    Sounds like it's been made of mozzarella, or something :eek:hmy:

    The 8v might be progress technologically speaking, but I envy the guy who bought my 1100...

    ;)
     
  3. pete roper

    pete roper GT Godfather!

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    Re:Got an 8V cam......

    We'll find out.

    I have to say that although my 1100 was good, my 1200 is better.

    Pete
     
  4. klaas123

    klaas123 Cruisin' Guzzisti

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    Re:Got an 8V cam......

    pete roper wrote:
    Great news Pete, that will give us some facts and hopefully an explanation of the failure.
    Thanks for doing this for us, afterall your 8V seems bullet proof!
    If there's a lot of money involved testing the parts I am willing to pay my share.
     
  5. Brian UK

    Brian UK GT Reference

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    Re:Got an 8V cam......

    Of course Pete, you will then have to remove same from your own bike to use as a comparison.:)
     
  6. pete roper

    pete roper GT Godfather!

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    Re:Got an 8V cam......

    Will I bollocks:cheer: :laugh: Mine'll come apart when it needs to. So far it shows no sign of needing to.

    Pete
     
  7. GT-Rx®

    GT-Rx® Administrator Staff Member GT di Razza Pura

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    Re:Got an 8V cam......

    "Sticky-ed" this topic in anticipation of Pete's info/analysis.
     
  8. pete roper

    pete roper GT Godfather!

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    Re:Got an 8V cam......

    Well, file will mark the worn bit. My thoughts on that were premature.

    OK. So today I took the cam and the tappet to the mint. The last time I went there was probably 8 years ago for a similar piece of investigation, that time on the splined centre of a surflex shallow spine clutch plate and a shallow spline clutch hub, but I digress.
    I had to fart about a bit as the security retard on the desk wanted a 'Name', and I simply wanted to talk to someone in the metalurgy dept.

    So I had to phone up, (on my mobile, from the foyer, because I wasn't allowed to use the internal phone system :blink:) but luckily the person I got through too was a fellow Bungendork who recognised my voice so the rest of the call was painless.

    Anyway she put me through to a lovely man called Eduardo Apoclevado who judging from his appearance and name was probably of Philipine origin, he's a metrologist and his main job is ascertaining the standards and HARDNESS of the dies they use for bashing out coinage. He's not an idiot, OK.

    I explained the problem and he said "No Worries, I'd love to take you back and show you but they've recently changed the security standards and you can't take *outsiders* into the Mint any more, sorry, but vive me half an hour and I'll go and test 'em right now." How many public/civil servants have you come across who are so accommodating????B) !!!!!!

    Anyway, I buggered off for some lunch and came back and he came out with the results.

    This was ascertained on a 'Beakers Machine' of which I know little apart from the fact it uses a diamond cutter to penetrate hardening It's an HV 30 if that means anything to anybody?

    Anyway the results were interesting. The cam is very, very hard. It has a rating of 736 on both test runs which equates to about 61 Rockwell. The tappet came in at 490 on the first test and 484 on the second, making it not as hard but still up around the 38-40RC which IMHO *should* be plenty hard for the tappet. If others with greater knowledge than me disagree please feel free to explain why?

    So to my mind it DOESN'T look like a hardness issue.

    More in a bit, gotta go cook.

    Pete
     
  9. klaas123

    klaas123 Cruisin' Guzzisti

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  10. pete roper

    pete roper GT Godfather!

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    Re:Got an 8V cam......

    OK, so it looks to me that the parts are hard enough to perform their alloted tasks so what else might be causing the failures?

    Well the obvious answer is of course lack of lubrication. There are a couple of glaring problems with that hypothesis though. Firstly the 'Trough' that the cam lobes dip in to is filled by spillage from the cam bearings, (There is a lot of oil being flung about at the top end.) If this flow was inadequate or interupted the cam would seize. In all the cases I've seen pics of and from talking to people who have had them apart the cam bearings on both the shaft and in the head and *scafolding* are perfect, untouched, pristine. So there HAS to be enough oil getting up there. Also although worn neaither cam lobes or the tappets have discoloured. In any situation where lack of oil was the cause you'd expect extensive overheating and significant blueing of componentry. Sadly this simply isn't the case. That too would seem to scupper my earlier suggestion of the tappet riding the cam as you'd expect discolouration in that situation too, bugger.

    One thing that is worthy of note is that at the base of the opening flank of the can there is damage inflicted by the tappet. Problem is of course we don't know if this occured before the failure commenced or if it was a result of of it??

    Another possibility is that the tappets although hardened correctly were inadequately radiused. Certainly the one I have had continued spinning, seemingly to the bitter end, but I've see pics of others that obviously stopped. Certainly if the radiusing was wrong or the edges of the tappet *foot* were too sharp this would tend to contribute to cam flank wear but the wear pattern of the tappet itself would indicate that this isn't the result of poor radiusing.

    Look, it is all quite baffling and this may well be the reason why Guzzi hasn't made any formal announcement. The factory engineers may be as baffled as the rest of us. So far the ONLY thing I can say with absolute cast iron certainty is that during the initial bedding in period the valve clearances DO close up radically. Whether this happens on all engines or only some of them I obviously don't know. What I do know is that on my bike and it seems on at least one other owned by a forum member, the clearances tightened up very rapidly to the point where I would of been concerned about damage occuring during that period. For that reason alone, and because it is so easy, I strongly recommend frequent clearance checks until the gaps cease to change. this might be within 1000Km, it might be at 10,000. Who knows, but its cheap, easy insurance.

    Incidentally when I left the Mint yesterday I was so wrapped up in my thoughts I forgot to offer Eduardo any remuneration for his time and effort. On the way home I realized this and phoned him up to apologise and ask if I could offer him something. His answer? "Nah mate, she'll be right. Glad to be of help." So I offered a bottle of nice wine "Jesus mate! You trying to get me sacked!? They'd have my head on a plate if they found me with booze at the mint!!!":laugh: So for all his time and effort it cost precisely nothing! My taxes at work! Brilliant!!!!:laugh: :laugh: :laugh:

    Pete
     
  11. Chuck in Indiana

    Chuck in Indiana Cruisin' Guzzisti GT Contributor

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    Re:Got an 8V cam......

    Pete said..Anyway the results were interesting. The cam is very, very hard. It has a rating of 736 on both test runs which equates to about 61 Rockwell. The tappet came in at 490 on the first test and 484 on the second, making it not as hard but still up around the 38-40RC which IMHO *should* be plenty hard for the tappet. If others with greater knowledge than me disagree please feel free to explain why?

    Yes, the cam is indeed hard at RC61. Now, be aware that I don't know carp about how hard the mating tappets *should* be, but RC 38-40 isn't squat. A spring, for heavinsake, is RC 45.:woohoo:
    Back in another lifetime, I was a tool and die maker, and was classified as a tool hardener for a while. RC 38-40 wouldn't cut it. (pun intended) :cheer:
    Chuck in Indiana
     
  12. pete roper

    pete roper GT Godfather!

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    Re:Got an 8V cam......

    Chuck in Indiana wrote:
    OK, I was hoping someone else would chime in, thanks Chuck. I was under the impression that 40 ish would be OK, obviously I'm wrong, unlike some I have no problem being wrong. So that is once more pointing us in a direction that is helpfull. Thanks.

    FWIW I did the tappets again on my 8V this mornings and they were all a trifle wide, (1/2 a thou) but the mnotor wasn't stone cold. they had all changed exactly the same amount though, judged by how much I had to twist the adjusters.

    Pete
     
  13. rguzz

    rguzz Tuned and Synch'ed

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    Re:Got an 8V cam......

    So we have a hard cam (RC61) rolling round a less hard tappet (RC40) in a bath of oil.
    This RC difference of 21 is substantial, given all stresses of operating hot engine, like a hammer on wood.
    There would be less wear if tappet was RC61, maybe it should be ?
    I found this site about tappet hardness<http://www.ameeraexports.com/tappet.htm>, worth a look.
    How all this results in failure of top end ( assisted by poor valve clearance checks), I'm not sure. Thoughts.......
     
  14. pete roper

    pete roper GT Godfather!

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    Re:Got an 8V cam......

    rguzz wrote:
    Sure its worth a look, won't open for me though. Got another link?

    Pete
     
  15. pete roper

    pete roper GT Godfather!

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    Re:Got an 8V cam......

    OK, got it open. So, their rating is 65RC so the Guzzi tappets are way too low at <40RC.

    So now we're getting somewhere. Methinks I'll order some new tappets, maybe just one, and get it replicated x4 in 60+RC and stick it in my bike and see what happens eh?

    Pete
     
  16. rguzz

    rguzz Tuned and Synch'ed

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    Re:Got an 8V cam......

    Yeah any kind of experimentation and monitoring is good.
    I suppose you could plot changes in valve clearances from new, as valves bed in, then tappets start to wear, plotting changes of micrometers against mileage. Each point on graph representing a check.
    Then you've got to decide how much wear to allow before tappet replacement.
    It's a lot of fannying about, but the devil is in the detail.
    Until a long term solution is found, then the dealer service schedule is probably no good.
    Robert.
     
  17. commando tod

    commando tod Cruisin' Guzzisti

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    Re:Got an 8V cam......

    I`ve been following this topic since the problem arose, and although it doesn`t affect my 1100, it was still disturbing enough to make me sit up and watch. I`m no metallurgist, and I know diddly squat about rockwell, but it does seem logical to a numpty like me that 1 hard surface trying to batter 1 soft surface, with clearances that diminish faster whisky in a glass and not allowing sufficient oil between the 2 to cool and lube and soften the impact is not condusive to a happy cam/tappet relationship. I`m glad that someone like Pete has taken the effort to find out what the hell is going wrong and lets hope Luigi at quality control at the tappet factory puts down the bottle of vino collapso and pays a little more attention to his work.
    Good on you Pete.
     
  18. WayneOrwig

    WayneOrwig GT Reference

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    Re:Got an 8V cam......

    pete roper wrote:
    If you have yours out, you should have them tested too. See if there is a dramatic difference in them. That would explain a lot, if a few batches didn't get hardened properly.
     
  19. RJVB

    RJVB GT Reference

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    Re:Got an 8V cam......

    Exactly what I was going to say (well, and that maybe you could take that file to your own cam :D )

    Back to basics a little bit... I haven't read what the mechanic in you thinks just looking at the parts you received — any thought on how/what failed? Also, any idea at what stage of failure this bike was?

    I'm a bit intrigued by the "the file will mark the worn bit". That's still talking about the cam, right? Could it be that not only are the tappets not hard enough, but the hardening of the cam isn't deep enough (= it's got a soft core) and/or not homogeneous enough?! That'd take a much longer time to test, but it could also explain why some bikes fail early, others late and yet others don't (or fail even later).

    (oh, and you know, us public/civil servants will sometimes go a long way just to do something we shouldn't be doing but that looks like what we ought to be doing :D ... but you could try meeting your new friend with that nice bottle on his way out going home ;) )
     
  20. pete roper

    pete roper GT Godfather!

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    Re:Got an 8V cam......

    Case hardening is never very deep rene, the core is always softer. I think my mistake was trying the file on an area adjacent to the worn bits of the cam lobe. Chances are it had either gone through the hardening or it was already heat affected, (although it didn't look it.) My mistake was guessing, and therefore supposing, that it was more likely to be the cam than the tappet tthat was soft. Once again more evidence that one should not work on supposition but wait for cold, hard facts.

    Unfortunately I can't similarly test one of my tappets until I have replacements in hand as the testing will damage them. Not an issue with a failed part but not something I want to do to something I haven't got a replacement for.
     
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