Lario ?

[jacksonracingcomau]

I bought a Lario a couple of months ago.

It was running fine, but nevertheless I took the engine apart.
That turned out to be a good decision, as I found that the camshaft and the tappets were completely knackered and the valve stems were stretched.
 
I think that the root cause of the Lario problems lies in a too hard valve spring, causing too much friction between the tappet and the cam, as there are two valves instead of one operated by each cam. 

Therefore the tip of the cam wears off, which results in a cam with a more square shape, which again results in uneven closing of the valve, which stretches the stem.

Of course this is just speculation, so I am open for other explanations.

What I have done is:

- Changed from a 12mm to a 14mm camshaft which gives 17% larger surface area.
- Changed to softer Nevada springs
- Used the best oil for the application, which I think is Royal Purple HPS 20W/50:  https://www.accessnorton.com/Oil-Tests/NortonOil.php

I have also changed from an 15 to an 19mm oil pump.

Regarding the oil restrictors between the cylinders and the heads, I am unsure as to whether 2 or 3mm are best. Any suggestions?

Ole

Interesting
By how much did valves stretch exactly, this would change spring preload of course as does the bottom retainer thickness and shims.
Then, what pressure do your new springs give  valve closed and at full lift ? I think this is what you call friction,
Installed height on yours ? was  huge variation on all I had, settling on figure was the game, factory manual misleading, especially the “extra preload “ later retainers .
Only ask because Nevada springs couldn’t work in my heads, not sure anybody else measures anything, you being the exception having ascertained a “valve stretch “ measurement, well done.
Not apparent on mine, valves hammered not stretched, exact opposite.

No oil feed problems afaik, mine orig restrictors/ locators and pump

[OKA]

>how many kilometers did the engine do ? This for future comparison when mine has been stripped
32000Km

>Where all 4 lobes on the cam / tappets shattered ?
Yes. Measured from the intake end they were down by: 1.2mm   3.2mm   2.0mm  1.1mm. So there is no pattern as to the exhaust cams being worse or better than the intakes.

>Do you still have the valves?
>Is it possible to carefully investigate them ?
Yes, I still have the valves. I will measure them and let you have the result. Unfortunately I don't know where each valve was fitted.

>Furthermore, your explanation is also applicable to the Intake valves, and there is NO indication for a high incidence of "valve-drop" for the Intake valves
This could be related to the thermal stresses for the exhaust valves?

>With regards to the oil restrictions: In my engine they are 2mm diameter
They are also 2mm in mine. Guzziology is a little vague on 2 contra 3mm.
In the RealClassic magazine there were an article about a 750 4-valve, where the owner had drilled them to 3mm. That gave too much oil at high revs.

Ole

[GoLario]

Gentlemen,
Thanks again for the exchange and the information

@OKA,

Of course I too would love to see the data, referred to by @jacksonracingcomau
We can combine them later on with my own findings

32000 Km, great, we have 2 engines with an almost identical service life
Did you measure the valve gaps, before disassembly ?
Mine were all greater then the prescribed 0.10 / 0.13 mm

So we are now really interested in the condition of the camshaft in my engine, right ?
I assume that the valve springs are the "factory" springs ?

Great to hear that you still have the valves; "they are important witnesses to the crime"
I hope you don't mind if we analyze them in the coming time in detail ?
Although you don't know the position where they were fitted, we will get important information from them
I have pictures of the valve heads available
For now I would like to know if they are welded, what the magnetic response is of the valve head, the valve stem and the valve tip
(of course in relative terms) and if the valves show signs that they were NOT properly closing anymore (you noticed valve stretch)

With regards to the thermal stresses, my "red herring" is becoming bigger and bigger
That is, at the higher temperatures  and temperature gradients in the 4-valve head, there is no margin left for the valves to accommodate
for adverse operating conditions
Where otherwise they would outlast another failure mode, now they fail first

With regards to the oil restriction:
I don't want to bother you already now with details, but I believe that the oil supply to the heads could become an important
element in the "valve-drop" story
 
Kind Regards,

Evert

[OKA]

I have measured the old valves:

In:    96.9    96.9   96.9   96.8mm
Out:  96.9    97.0   96.7   96.7mm

According to the manual they should be 95.35-95.65mm In and 95.25-95.55mm Out, but I find it hard to believe as the new ones are 96.8mm In and 96.5mm out. Also I don't think that they have stretched more than 1mm, especially as they fitted nicely in the guides.

They were fitted with lash caps, but I think the caps are retrofitted, because the valve stems had depressions from the valve adjuster. The biggest depression was on the 97.0mm exhaust valve and the smallest on the 96.8mm inlet.

The inlet valves, new and old, are magnetic all over.
The old exhausts have magnetic stems and non-magnetic heads.
The new exhausts are not magnetic at all.

I dont't know what the installed height was and I can't check it as the seats have be recut, but the height is 36mm now.

>Did you measure the valve gaps, before disassembly ?
No

[GoLario]

Hello @OKA,

Thank you for your efforts

With regards to the valve length:
All data I have confirm the data in your manual
If the valves were stretched, I would NOT expect the Intake and the Exhaust valves have identical values
The 8 values have a mean value of 96.875 mm, with a range of 0.300 mm
Allowing for some wear on the tips, I would think this looks like manufacturing tolerances
That is, there is no stretching at all

The magnetic responses for the old valves are identical to my findings
Very worthwhile information, as they fit into the picture that I believe is emerging

According to my data, the original valve springs are 36.3 mm at a pre-load of 26.2 Kg ( valve closed )

How did you get hold of a good 14 mm camshaft and the 20 mm tappets (followers) for this camshaft ?

Kind Regards,

Evert


 

[injundave]

I have a Lario which I have almost finished rebuilding. It dropped an exhaust valve in the left cylinder, destroying the head and piston and damaging the cylinder. The valves now look like this:





The inlets are on the left. Despite being bent they are both in one piece. They are strongly magnetic on stems and heads.
The exhausts are strongly magnetic on the stems and slightly magnetic on the heads.

The cam was pitted on one lobe and I had it welded and reground and the followers refaced by a cam specialist at a cost of about $400. Cheaper than a new cam!

[OKA]

GoLario:

>All data I have confirm the data in your manual
>The 8 values have a mean value of 96.875 mm, with a range of 0.300 mm
>That is, there is no stretching at all

And from my previous post:
According to the manual they should be 95.35-95.65mm In and 95.25-95.55mm Out

I can not follow your reasoning here. According to the manual they should be more that one millimeter shorter.
Unless of course you are comparing them to the new valves, but they are not an original Guzzi part.

I bought the new cam here: https://guzziepiushop.de/

They could not supply new tappets, but they offer a service, where they take the innards from the old tappet and replace it in a tappet from a newer model (I think), so that I ended up with almost new tappets.

Ole

[GoLario]

Hello,

@injundave,
Fantastic
Thank you for your help
Allow me to come back to you in one of the coming days
Thank you

@oka,
Apologies if my communication was / is poor
What I wanted to say is, that the data I have found so far confirm the data you found in your manual
Therefore your new valves are indeed more then 1 mm longer
ALL 8 valves
And the lengths of the new valves are within a very narrow range
BOTH Intake and Exhaust valves
IMHO it is highly unlikely that a set of 4 Intake valves and 4 Exhaust valves have stretched that evenly
That is why I am tempted to believe there has been no stretching, and that what we see is simply the manufacturing result
We could go back to Guzziepiu and clarify this matter
If you need help, let me know, they are German and I live in Germany
I hope this helps

Thanks for the information on the tappets

Kind Regards,

Evert

[GoLario]

Hello @OKA,
Sorry
Forget everything I have said so far
I realize I messed things up
Allow me to come back to you in one of the coming days
Once again sorry

Regards,

Evert