8V Failure info.

[pete roper]

Got a cam & tappets that's failed.

File will mark the cam.

Off to the Mint this week.

Pete

[Steve uk]

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

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

[pete roper]

We'll find out.

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

Pete

[klaas123]

pete roper wrote:

That's failed. and a tappet.

File will mark the cam.

Off to the Mint this week.

Pete

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.

[Brian UK]

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

[pete roper]

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

Pete

[GT-Rx]

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

[pete roper]

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 ) 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

[klaas123]

The HV-30:

http://www.metalkorea.or.kr/Measurable/hv30.html

[pete roper]

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:

Pete