8V Failure info.

[Penis Rotor]

Doesn't show you what happens in the heads though. I'd better take some pics.

pete

 

[Phang]

Thanks Pete, appreciate if you can show how the oil goes around the inner front stud and the respective mating side on the cambox. This is one of the areas that I am unable to figure out and visualise.

p/s: get something to support your camera or someone with a steady hand :mrgreen:

Phang

 

[Brian UK]

I wouldn't know how valid this information is but our sister forum "Guzzitek" has this document concerning the oil system.
http://guzzitek.org/documents/divers/Motor1200_8V_Course_(GB).pdf

The pump has 2 different delivery lines with a checklist what is being fed.

According to this the high pressure inner pump lubricates the heads. :? But stranger things have appeared in English translations of the Italian original.

 

[Penis Rotor]

Well, I went and closely inspected my 'Loose' head and Paul and Brian are right. The cooling side ONLY provides oil to the galleries around the exhaust valves. The actual lubrication for the camboxes comes up the studs! I was wrong.

Looking at the casting there looks to be a cross drilling from the head feed to the stud gallery. Taking the head into fiull sunlight and having a really good squint there is no connecting drilling to the stud gallery. That means that the oil not only for the bearings but also the cam bath HAS to come up the studs from the crankcase. And that opens up a whole different can of worms.

At the bottom end the high pressure circuit provides lubrication for the mains and big ends and the under-piston sprays but NOT for the bearings for the idler shaft which runs on rolling ellement bearings fed, (Presumably.)by splash. There must then be galleries cross-drilled to the stud galleries at the front and back to deliver oil to the camboxes.

One thing this does tend to do is blow the 'Blocked pipe' theory to hades. Bugger!

Pette

 

[hemelguzzi]

Pete, please inform me of what make 10/70 oil you use and at what mileage you change it. Thanks in advance.Just trying to find way of keeping my stelvio instead of selling it as you suggested.

 

[Penis Rotor]

A type you won't probably be able to get in England. Also I don't think the type is important. It HAS to be a real top of the range full synth to put up with the heat but as long as its able to do that I don't think that manufacturer or even to a lesser extent viscosity breadth is *that* important.

To me its looking more and more as if the failures may be more related to oil starvation rather than a physical problem with the actual materials. As I've said before I have yet to see a bike that has had a secondary failure that has been maintained correctly but the fact that the oil for the camboxes comees from the high pressure circuit whiich is fed from the block up to the heads via the stud galleries opens up a whole other raft of possibilities as far as why the damage is occuring.

Really though, until I get an engine which has failed onto my bench for a complete tear down I'm as much in the dark as anybody else! I DO now trnd to think though that simplr replacing the worn out bits will be essentially fruitless. The fact that the vast majority of 8V motors suffer NO problems at all reeks of a manufacturing fault or an assebly fault to me rather than this idea that the engine is somehow 'Flawed' by design.

Using a different variety of oil *might* delay a problem but in and of itself I don't believe it will effect a miraculous 'Cure'. For that we have to first identify the problem and that is what is proving so ellusive.

Pete

Pete

 

[Mi_ka]

... the oil for the camboxes comees from the high pressure circuit whiich is fed from the block up to the heads via the stud galleries ...

So, the oil is pressed up the same holes that the studs come through to compress the cylinder-head assembly on the engine cases? Are the studs "wet" by oil around them or do I get it wrong?
If so, maybe minor misalignments of gasket holes or studs could pose obstacles to flow leading to minor starvation which causes the problem on the long run?
Are the cam bearings lubricated under pressure or just bath lubed by the supplied oil?

 

[Penis Rotor]

Cams spin at 1/2 crank speed, they have to be pressure fed. As for the misalignment issue? Can't be gaskets blocking the flow as the gallery studs are doweled.

Pete

 

[Mi_ka]

Cams spin at 1/2 crank speed, they have to be pressure fed

"Elementary, my dear Watson"...
Still I do not get how the pressure line travels beside the studs. A picture/diagram would help my peanut brain.

 

[pauldaytona]

Cams spin at 1/2 crank speed, they have to be pressure fed

"Elementary, my dear Watson"...
Still I do not get how the pressure line travels beside the studs. A picture/diagram would help my peanut brain.

In the head where the oilpressure is goes a hole to the stud bore. The bore is fi 10mm, and stud is 9mm, then there is always an average 0,5mm space around the stud. even if it's not centerd. Then one side has some more, the otehr side less space. It seems little, but you don't need much, and do some calculating.
Then the alu part that houses the cams and rockers, has a hole in the stud bore, from there the oil goes to the bearings.

 

[Phang]

Hi Mi_ka, this is an example from a BMW airhead.

------------------------------------------------------------------------------------------------------------------

Pete, this is getting interesting... :mrgreen:

Assuming this is due to oil starvation to the cambox couple with your finding below:-

That means that the oil not only for the bearings but also the cam bath HAS to come up the studs from the crankcase. And that opens up a whole different can of worms.

Pette

It seems like only the cam followers/tappets and/or cam lobes are not getting the oil, I presume the bearing surface of the rocker arm shafts and camshafts are fine in an engine that toast its cam followers.

That means something is wrong with the oil gallery WITHIN the cambox that feeds the cam follwers/tappets.

When I re-read the topic “Strange sound coming from LH cylinder head 8” by klaas123, you mentioned this in page 4:-

Can't find a thing wrong, everything seems in good condition.

The lash caps on the ends of the adjusters are comprehensively f@cked! and there is irregular wear on the tappet heads. My guess is that for some reason the *upper* tappet in pic #2 has been not turning correctly, looking at it it appears it may not of been radiused properly or the cambox tunnel it runs in has caused it to 'Grab' at some point. That tappet is showing a clearly defined wear ring where the HLD treatment has been degraded and erroded. You'd probably need more accurate measuring equipment than most of us have to check the radius damage but I'll betcha that the noise is due to the uneven nature of the radius due to the wear on the HLD coating.

With damage like that to the lash caps you'll never get an accurate valve lash adjustement which will also contribute to the top end noise.

I'm hoping that the 'I can't see anything wrong' comment was a joke?

Pete

From the pics posted by Klaas123, it looks like there are holes drilled at the side of the cam follower bore for pressurized oil to keep the follower “afloat” and spinning in the bore and the excess oil will be fetched by the cam bath directly below. Could it be the culprit?

Phang

 

[DanPez]

If oil starvation may be an issue and assuming that the passages are manufactured similarly for these engines I was wondering if there is a possibility to measure the oil pump pressure. (edit: on the bike while running)
Any idea of the pressure values at diff rpms and /or where to plug the gauge?

Looking at the parts explosion diagram the oil pump is driven by a drive gear connected to the crankshaft .
This gear is torqued at 200Nm.
Could that have loosen up?
Would't be the first time!!!
Added https://www.guzzitech.com/Griso8V/Tech/8Vtimingnut-003-2008.pdf

 

[Brian UK]

As I think I mentioned way back in this thread, Corsa Italiana in the UK had one Griso which was dry on one head. A new oil pump cured it.
Old pump was sent back to Guzzi,so no idea what might have been wrong with it.

 

[Penis Rotor]

But why would a faulty pump only fail to oil one side? It doesn't make sense???

Pete

 

[DanPez]

But why would a faulty pump only fail to oil one side? It doesn't make sense???
Pete

Thinking out loud .....?&%%*
The high pressure oil pump outlet is centered at the bottom radius of the crankshaft .... spraying upwards...towards the heads.
The oil passage lenght, going to the head, of the right side should be equal to the left side .... presuamably.

Looking at the engine from the front ....the pump rotates CW therefore the crank rotates CCW.
Is there a bushing between the crankcase and crankshaft? (Perforated to let the oil pass)

Just a thought are the right tappets failing more than the left ones?
I gotta get a life :lol:

 

[Penis Rotor]

There is no oil being srayed anywhere Dan, apart from the undersides of the pistons. It's pumped through galleries to the bearing surfaces like water through a plumbing system. Nor are there any 'Perforated bushes'.

Pete

 

[Mi_ka]

One more extravagant theory:
Looking at the pictures I think it is a located thermal failure. Maybe oil is fed and provides lubrication but not enough quantity goes through the space to provide cooling for the tappet cam lobe area of contact so thermal loads accumulate leading to the damage. So, oil starvation of shorts.
Any possibility of the camshaft having tighter than designed clearances towards its box bearings so the supplied oil has trouble flowing in the designed quantity as it follows a path of less resistance toward the main crankshaft circuit etc? Maybe the problem can be elsewhere lower in the engine where a "less resistive" path is provided and the outcome is less flow to the heads.
Or maybe some engines assembled to the low end of the camshaft/camshaft bearing tolerances have "higher flow resistance" when cold so the thick cold oil fails to travel in designed quantity through the heads and escapes lower through the circuit. If we add that the overpressure valve of the oil pump actuated by the cold thick oil reducing even more the total flow then a combination of factors may apply to a "bad bunch" of engines while the design is essentially sound when all the strange factors do not coincide. Of course this would suggest a higher rate of failure for bikes ridden cold for short distances or maybe flogged while still cold.
(Maybe I should become a fiction writer... )

 

[DanPez]

There is no oil being srayed anywhere Dan, apart from the undersides of the pistons. It's pumped through galleries to the bearing surfaces like water through a plumbing system. Nor are there any 'Perforated bushes'.
Pete

My mistake ....
You have to excuse me I get too excited with these diagnostics :woohoo:
I meant to say "The high pressure oil pump outlet is centered at the bottom radius of the crankshaft .... flowing upwards...towards the heads."

The bushing I was looking at was on the "Crank Case I" diagram (item 1) .... the crankshaft bushing looked kind of holy to me :laugh: . ........ I maybe wrong.
http://www.guzzitek.org/parts_list/gb/1200/Stelvio1200_2008_PL(GB).pdf


Was wondering if postioning that bushing may influenced the flow. ..... just a thought.

 

[Brian UK]

I can't even attempt to explain anything, the only possibility I could think of was that there may have been a partial blockage on one side, and low oil pressure too. But as we don't know what happened in the oil pump, who can say.
Seems to me there is little point in guessing at what is happening on these few bikes, until someone like Pete has one in his sticky hands to look at properly.

 

[draidt]

I can't even attempt to explain anything, the only possibility I could think of was that there may have been a partial blockage on one side, and low oil pressure too. But as we don't know what happened in the oil pump, who can say.
Seems to me there is little point in guessing at what is happening on these few bikes, until someone like Pete has one in his sticky hands to look at properly.

That's my point I made earlier exactly how many bikes ? No one knows I suspect except Piaggio. The 8V has been available in the US for a while now and has a track record of motors NOT going tits up with cam failures after the recall has been done something changed.