Author Topic: Lario ?  (Read 1782 times)

Offline Peter949

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Lario ?
« on: November 07, 2019, 04:26:36 PM »
Recently a nice looking, but non-running 1985 Lario came up for sale in my area.
Does this bike typically have reliability problems with what I believe is a 4 valve cylinder head. 


image upload
« Last Edit: November 07, 2019, 04:27:18 PM by Peter949 »
Peter

1984  Cali II
2012  Stelvio
Aprilia 125 Sportcity

Offline Mayor_of_BBQ

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Re: Lario ?
« Reply #1 on: November 07, 2019, 04:34:05 PM »
check the rebuilds & restorations area for Chuck's thread... you wont be sorry. It should be on the first or second page.  Also search for posts by iceblue ... they have the information you seek.
1971 Ambo *barn fresh*
1976 Robin *beer runner*
1984 V65 *the astronaut*
2007 Breva 1100 *the prospector*
2014 DR650 *starts every time*

pete roper

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Re: Lario ?
« Reply #2 on: November 07, 2019, 04:35:13 PM »
Yup. Not the same issue as the 8V flattappet motors but they are a ticking time bomb.

Martin, (Jacksonracing) reckonshe's finally made one reliable and there are a few other fixes of dubious effectiveness out there. Check before you buy that it hasn't dropped a valve.

Pete

Offline analog kid

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Re: Lario ?
« Reply #3 on: November 07, 2019, 05:48:51 PM »
I sent the owner a note this afternoon asking for more info on the "non-running" part.
He hasn't answered yet..... :evil:

Who would have thought there were 2 Larios in the Toronto area.  ( I never figured I'd see ONE!) . I looked at a red one for sale in 05.
90 Mille GT
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84 LeMans lll (project)
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Re: Lario ?
« Reply #3 on: November 07, 2019, 05:48:51 PM »

Offline jacksonracingcomau

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Re: Lario ?
« Reply #4 on: November 07, 2019, 06:42:53 PM »
All bets are dropped valve, get pics rocker boxes off, will be obvious
But even if it hasnít yet, cam and followers will need looking at, fix is only methodical build.
Engine is a little hooter, I have been a BB one eyed devotee for nearly 42 years but last 12 months the 650 8 valve has been my go to bike, even two up travelling, has done Tasmania 2 up twice now, about to go again.

Donít let internet problems get in the way, way too many opinions out there, if you can use basic measuring tools ( only tool I bought was a cheap valve spring measuring one ; something I should have owned for 40 years )
Get your clearances as per design, blueprint is good word. Robert becomes your motherís brother.

Costs time and a little money, probably not ever saleable for any great amount but value is in twisting the agitator, specially if the original price is scrap value.
Prise mine from my cold dead fingers

Offline Chuck in Indiana

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Re: Lario ?
« Reply #5 on: November 07, 2019, 06:56:47 PM »
Quote
specially if the original price is scrap value.
:grin: Yep, at that price you can afford to tinker with it. It is a *fun* engine. I would have loved to see if I could make it reliable, but the Aero engine became available.. and I decided that would be even more fun.
Chuck in (Elwood) Indiana/sometimes SoCal

02 Scura RC
87 AeroLario
79 G5
95 Skorpion tour
 
I think senility is going to be a fairly smooth transition for me..

Online huub

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Re: Lario ?
« Reply #6 on: November 08, 2019, 12:29:17 AM »
if you dont mind doin a rebuild before riding it , go for it!
mine is in daily use, has over 120.000 km on the clock since the last rebuild.
with modern valves and upgraded valve springs the reliability is no issue
i have a fleet of other bikes availabe(guzzi le mans , ducati's) , but end up doing virtually all my riding on the lario.
for me it hits the sweet spot , it is light and nimble , enough power to have fun , and you can ride flat out without killing yourself.
« Last Edit: November 08, 2019, 05:23:57 PM by huub »

Offline Peter949

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Re: Lario ?
« Reply #7 on: November 08, 2019, 07:51:59 AM »
I found this post from a fellow in NZ:

V65 Lario was my introduction to the world of Moto Guzzi some 20 years ago

 My understanding of the valve problem goes like this:-

 The relatively heavy valve springs coupled with a somewhat soft material used in the valve stems, resulted in the ends of the valve stems mushrooming with use. This resulted in the valve adjuster being unable to slide on the end of the valve stem, causing the valve stem to flex back and forwards, eventually fracturing. This of course resulted in the valve heads dropping onto the top of the piston, destroying that side of the motor.

 The factory fix for the problem was the issuing of a set of hard steel lash caps for the valve stems.

 I fitted the lash caps, and also softer valve springs (Suzuki GN250). The motor seemed to be much happier with the softer valve springs. Fitting these caused a small problem, as the GN250 springs are slightly larger in diameter than the oringinal Lario ones. This was overcome in the following maner. I obtained spring retainrs from 2 different Suzuki models. From memory these were the GN 250 and a GSX250. One retainer was a properly machined steel retainer, that fitted over the valve guides and provided a seat against the head that matched the increased spring diameter. The other retainer was a pressed steel one (like a bowler hat) that also matched the increased spring diameter, but significantly was exactly sized to fit over the Lario spring retainer without any play at all. This allowed me to use the standard Lario valves and collets, as the collets were still fitting into the Lario retainers.

 
Peter

1984  Cali II
2012  Stelvio
Aprilia 125 Sportcity

Offline Chuck in Indiana

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Re: Lario ?
« Reply #8 on: November 08, 2019, 08:03:09 AM »
Chuck in (Elwood) Indiana/sometimes SoCal

02 Scura RC
87 AeroLario
79 G5
95 Skorpion tour
 
I think senility is going to be a fairly smooth transition for me..

Online huub

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Re: Lario ?
« Reply #9 on: November 08, 2019, 09:31:02 AM »
I found this post from a fellow in NZ:

V65 Lario was my introduction to the world of Moto Guzzi some 20 years ago

 My understanding of the valve problem goes like this:-

 The relatively heavy valve springs coupled with a somewhat soft material used in the valve stems, resulted in the ends of the valve stems mushrooming with use. This resulted in the valve adjuster being unable to slide on the end of the valve stem, causing the valve stem to flex back and forwards, eventually fracturing. This of course resulted in the valve heads dropping onto the top of the piston, destroying that side of the motor.

 The factory fix for the problem was the issuing of a set of hard steel lash caps for the valve stems.

 I fitted the lash caps, and also softer valve springs (Suzuki GN250). The motor seemed to be much happier with the softer valve springs. Fitting these caused a small problem, as the GN250 springs are slightly larger in diameter than the oringinal Lario ones. This was overcome in the following maner. I obtained spring retainrs from 2 different Suzuki models. From memory these were the GN 250 and a GSX250. One retainer was a properly machined steel retainer, that fitted over the valve guides and provided a seat against the head that matched the increased spring diameter. The other retainer was a pressed steel one (like a bowler hat) that also matched the increased spring diameter, but significantly was exactly sized to fit over the Lario spring retainer without any play at all. This allowed me to use the standard Lario valves and collets, as the collets were still fitting into the Lario retainers.

the valves currently available dont need the lash caps , they have stellited tips.
instead of suzuki valve springs use guzzi valve springs  you wil find enough info on this forum.

Offline GoLario

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Re: Lario ?
« Reply #10 on: November 08, 2019, 02:35:55 PM »
Gentlemen,

I decided to bring a Lario back on the road
I have no issues  with (the costs of) modifying the valve train
But what then is the preferred route ?
I believe there are quite a few very knowledgeable people around,
but unfortunately their proposals, their results and the reasoning behind them
do not converge
(in my limited understanding)
I have a feeling that what is lacking is a solid description of the variables with
regards to how the engine has been operated, combined with the modification
Thing like generally high / low RPM, yes / no red line RPM, yes or no frequent use,
long / short distances, oil quality, additives, etc.
This especially keeps me busy, because of the following
I accept that the design might be flawed, that (too) many engines destroyed themselves,
that eventually all engines will destroy themselves, but ..... why is it that so many last so much longer ?

Kind Regards,

Evert


Offline Chuck in Indiana

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Re: Lario ?
« Reply #11 on: November 08, 2019, 03:44:04 PM »
Gentlemen,

I decided to bring a Lario back on the road
I have no issues  with (the costs of) modifying the valve train
But what then is the preferred route ?
I believe there are quite a few very knowledgeable people around,
but unfortunately their proposals, their results and the reasoning behind them
do not converge
(in my limited understanding)
I have a feeling that what is lacking is a solid description of the variables with
regards to how the engine has been operated, combined with the modification
Thing like generally high / low RPM, yes / no red line RPM, yes or no frequent use,
long / short distances, oil quality, additives, etc.
This especially keeps me busy, because of the following
I accept that the design might be flawed, that (too) many engines destroyed themselves,
that eventually all engines will destroy themselves, but ..... why is it that so many last so much longer ?

Kind Regards,

Evert
First, welcome to WG, Evert.  :thumb:
As far as I'm concerned, the thread by Martin (jacksonracing) that I posted above is the best "fix" for the Lario 4V that *I* know of.
Huub is beginning to rack up some miles with his build.
I did a thread in the projects area that may be somewhat useful.. Lario rehab.. although photoblockit has blurred all the pictures.  :evil:
Chuck in (Elwood) Indiana/sometimes SoCal

02 Scura RC
87 AeroLario
79 G5
95 Skorpion tour
 
I think senility is going to be a fairly smooth transition for me..

Online huub

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Re: Lario ?
« Reply #12 on: November 08, 2019, 05:19:47 PM »
Gentlemen,

I decided to bring a Lario back on the road
I have no issues  with (the costs of) modifying the valve train
But what then is the preferred route ?
I believe there are quite a few very knowledgeable people around,
but unfortunately their proposals, their results and the reasoning behind them
do not converge
(in my limited understanding)
I have a feeling that what is lacking is a solid description of the variables with
regards to how the engine has been operated, combined with the modification
Thing like generally high / low RPM, yes / no red line RPM, yes or no frequent use,
long / short distances, oil quality, additives, etc.
This especially keeps me busy, because of the following
I accept that the design might be flawed, that (too) many engines destroyed themselves,
that eventually all engines will destroy themselves, but ..... why is it that so many last so much longer ?

Kind Regards,

Evert

Hi Evert
the engine design is not that bad  but Guzzi cheaped out when choosing valve springs  using the same springs they had in stock for the 2 valve engines ( even for the 2 valve engines they were too stiff)
so basically the valves were torn apart and the camshaft was smashed because of the extreme spring pressure.

You are unlikely going to find a definitive answer in a forum   Basically nobody has the opportunity to do side by side testing of differnt strategies  and still has time to make a meaningfull amount of kilometers to test them.
lets face it  even the guzzi factory failed to do proper field tests, a lot of lario's dropped valves while still in warranty
i havent seen a lario with more km than mine yet ( total should be close to 160.000 km (100.000 miles ),  120.000km after the last rebuild)
but that does not mean the solution i chose is the only sucesfull solution.

With a engine like this you are on your own  you can choose whatever seems  a plausible solution for you.
i had the same problem with my nuovo falcone, decided on a solution,  only to have another dropped valve 70.000 km later .
so with the falcone i am back at the drawing board coming up with a new set of modifications.

Huub

Offline jacksonracingcomau

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Re: Lario ?
« Reply #13 on: November 09, 2019, 12:45:03 AM »
I posted a thread why do larios drop valves
Answers were interesting and varied, only one made sense to me
But I decided to measure, keep measuring and leave no room for error
As if it were race engine, modified with bits that weenít in any manual.

Bottom line, I think some may get away with buying bits from a shopping list off the net, some will not
I had two rebuilt engines both had no hope of survival, builders did not understand physics of engine.
I had one oe cylinder head, not modified at all, that also wouldíve gone bang without question.

No dispersal to owners
1 Rae , a dear friend, used as was for 10 years and 80Kkm (50K miles) just didnít give it noise
2/ CiI, got bike badly fixed, tried but Aero engine came up and who wouldnít?
Thanks to both, maybe especially Pete at Reboot,, had the oe rh head, answers were there

I use Phil Irvingís Tuning for Speed as my bible, not much changed since he wrote it, if anything things are easier

It is not rocket science, nor is it a walk in the park, I think I could list the only important things but did so much more to make absolutely certain, I wonít.
Starting with factory build, untouched by amateurs would be lovely but unflking the errors is the game.
Design was brilliant, execution pathetic, attempted fixes just ridiculous.

For OP, If bike has dropped valve, as is likely, there is a simple, relatively cheap fix, engines from crashed v7 or v9 drop in, quite a few on here, listing entire process
You choose efi or carbs, ignition kits available too, will be as reliable as modern sbís are, no, not the 9k rpm giggle maker the 8v is but usable daily with no issues.

Added bonus, if it dropped left side valve, I will buy right cylinder head and all rocker gear & pushrods giving you a chunk towards v7 or v9 engine ó off ebay ?
« Last Edit: November 09, 2019, 04:15:39 AM by jacksonracingcomau »

Offline GoLario

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Re: Lario ?
« Reply #14 on: November 09, 2019, 05:20:13 AM »
@Chuck, @Huub, @Jackson,
Thank you very much for your replies
Combined with the very well documented efforts of IceBlue
I can see the multifaceted aspects with regards to the valve train
I have already found the "bible", Tuning for Speed; thank you @jackson
My formal training is Chemical Engineering, but I will try hard to familiarize myself
with the content
I also realize that as a start, I have to appreciate that the Guzzi engineers were
knowledgeable, and phrasing questions keeping that in mind
One of them:
Why did Guzzi specify 0.10 mm gap for the Intake and 0.13 mm for the Exhaust, whereas
they increased this to  0.15 mm respectively 0.20 mm for the 2V's ?
Could it be that these gaps have become "super critical" for the Lario ?
When the valve train is so much higher, mechanically stressed, could it be that the dynamic behavior
does NOT allow for any free play, before engagement of the components DOES take place
(For example, I take it that Followers are called just that because they should follow smoothly)

I have "seen" this issue of uncontrolled engagement being discussed in the context of sprag clutches that were
destroyed in no time
They are / were in MV Agusta's !

Thank you for your patience; you are educating a Guzzi enthusiast who wants to get a Lario back on the road,
and lasting

Kind Regards,

Evert
 


Offline jacksonracingcomau

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Re: Lario ?
« Reply #15 on: November 09, 2019, 07:18:34 PM »
@Chuck, @Huub, @Jackson,
Thank you very much for your replies
Combined with the very well documented efforts of IceBlue
I can see the multifaceted aspects with regards to the valve train
I have already found the "bible", Tuning for Speed; thank you @jackson
My formal training is Chemical Engineering, but I will try hard to familiarize myself
with the content
I also realize that as a start, I have to appreciate that the Guzzi engineers were
knowledgeable, and phrasing questions keeping that in mind
One of them:
Why did Guzzi specify 0.10 mm gap for the Intake and 0.13 mm for the Exhaust, whereas
they increased this to  0.15 mm respectively 0.20 mm for the 2V's ?
Could it be that these gaps have become "super critical" for the Lario ?
When the valve train is so much higher, mechanically stressed, could it be that the dynamic behavior
does NOT allow for any free play, before engagement of the components DOES take place
(For example, I take it that Followers are called just that because they should follow smoothly)

I have "seen" this issue of uncontrolled engagement being discussed in the context of sprag clutches that were
destroyed in no time
They are / were in MV Agusta's !

Thank you for your patience; you are educating a Guzzi enthusiast who wants to get a Lario back on the road,
and lasting

Kind Regards,

Evert

Miles away from the orig problem but I see no issue in + a thou if you want a bit more tappy noise ( apart from losing some lift )
Mine stays happy at .004 and .005 ď
5 come in under your 13 french things, 6 I could hear
Short pushrods are good for stability but if I ever build the really hot one, may well make new pushrods from scratch, capable of 10k rpm +

Online huub

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Re: Lario ?
« Reply #16 on: November 10, 2019, 02:53:18 AM »
Dont expect guzzi to have engineered that much on the lario
it was rushed into production to keep up with the performance of the rest of the market.
to save costs parts were sourced from other models, even when it made no sense for this application (like valve springs, carbs,  camshaft)
it was just buit for a couple of years and wont be remembered as their best product ever.

so current knowlegde of the valve system is from amateur engine builders.
the guzzi camshaft is pretty crude, has no quitening ramps so valves are basically smacked open.
i dont think a extra 0.05 mm will change a lot about that situation.   
i prefer to keep the tappets on the loose side, but that is just my personal preference

Offline Chuck in Indiana

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Re: Lario ?
« Reply #17 on: November 10, 2019, 06:17:09 AM »
Megacycle made a cam for the Lario with oil delivery holes. They wiped lobes, too.  :cool:
Chuck in (Elwood) Indiana/sometimes SoCal

02 Scura RC
87 AeroLario
79 G5
95 Skorpion tour
 
I think senility is going to be a fairly smooth transition for me..

Offline GoLario

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Re: Lario ?
« Reply #18 on: November 10, 2019, 09:32:25 AM »
Gentlemen,
Thank you again for being patient with me and sharing your knowledge and views
As explained to you, I would like to understand things better (then I do right now)
So far I understood that the "Lario" cam is the same cam as used in the V2 engines,
being the 12 mm width cam or the later 14 mm cam
@Huub, you are saying that none of the cams, throughout all the models, have ramps ?
Besides trying to establish myself a lift curve (the profile) of the cam in my Lario,
does anyone of you have already a lift curve ?
That would be great to have as a reference and to check the quality of my own exercise
I promise you I will continue studying, as to become less of a loose cannon

Thank you and kind regards,

Evert

Offline GoLario

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Re: Lario ?
« Reply #19 on: November 10, 2019, 10:19:06 AM »
Hello @jacksonracingcomau,

If you are looking for a RH cylinder head I have seen there is a used one around
BUT, they ask 300 Euro !!

Regards,

Evert

Offline jacksonracingcomau

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Re: Lario ?
« Reply #20 on: November 10, 2019, 10:42:39 PM »
Dont expect guzzi to have engineered that much on the lario
it was rushed into production to keep up with the performance of the rest of the market.
to save costs parts were sourced from other models, even when it made no sense for this application (like valve springs, carbs,  camshaft)
it was just buit for a couple of years and wont be remembered as their best product ever.

so current knowlegde of the valve system is from amateur engine builders.
the guzzi camshaft is pretty crude, has no quitening ramps so valves are basically smacked open.
i dont think a extra 0.05 mm will change a lot about that situation.   
i prefer to keep the tappets on the loose side, but that is just my personal preference

ODD
All parts books and bits I have show valves, springs, retainers etc all unique to Lario, basically complete top ends
Have only read on here of people using 2v valve springs, I did buy some but couldnít of worked in my heads, as the oe ones couldnít, someone didnít notice the rocker arm ratio and actual valve travel.
Cam lift /pushrod travel not same thing as valve travel in this case
Camshaft was 2v one, I did use just to prove design but is very lame by any std I know, only because of rocker ratio and increased valve area does it work and rev so high.
One I want to use is more like you describe, a brick on a stick, then it will proper boogie

The engine design imho was up there for itís time, blueprinting that makes a very usable thing, like a v7 up to 6 k, then dr jeckyll comes in.
Problem as I see it, then as up tp now, the designer who gets the most cash is not in the engine room
Money was spent on plastic, the new space age styling was priority, shame
Finally v85 seems to be engine finished first, been a long wait
Hello @jacksonracingcomau,

If you are looking for a RH cylinder head I have seen there is a used one around
BUT, they ask 300 Euro !!

Regards,

Evert

Thanks but ideally I find whole unmolested Lario and chuck v7 or v9 in that, ideal for someone who wants the look of it without concern for or expense of engine

I get engine to play with, if a left side dropped am ok for bits. If another badly fixed, another can of worms

Or someone on here wants to do it as I suggested to OP, guessing he doesnít know engine damage yet but looks perfect one to do it too.

RH head Iíd buy (maybe not 300 tho ) but donít want another badly welded up one, have some of them already, virgin I want. No rush

Offline GoLario

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Re: Lario ?
« Reply #21 on: December 01, 2019, 08:53:50 AM »
Hello,

I have taken off the heads from my Lario and the good news is that the valve train components look good
Didn't take out the valves yet, and don't know yet how the camshaft will look like
But, as I want to understand the "valve drop issue", I examined the valves closely for their magnetic response
To me, the findings are intriguing and could hold important clues
Now, ALL Intake and Exhaust valves show a magnetic response for Valve head and valve stem
ALL Intake valves show a strong response for head and stem
The Exhaust valves show a similar strong response for the valve stem
HOWEVER, the response for the valve heads is MUCH LESS
AND, the response in the center of the head is very weak, stronger towards the circumference
( A magnet will shift from the center towards the periphery )

Does anybody know what the material of the original valves, that Moto Guzzi used, is ?
What can we possibly learn from the above observations ?

Thanks for your help

KInd Regards,

Evert

Offline moto-uno

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Re: Lario ?
« Reply #22 on: December 01, 2019, 06:47:47 PM »
Welded valves have been the norm in many engine makers for years , good old high speed spin welding to attach stem to head ( hence different magnetic properties)
Have no idea about the Lario engine , but , if it's relevant I've had very good luck and longevity from Kibblewhite valves in my Le Mans 2.
I had no idea that model had such a checked history . Peter

Offline jacksonracingcomau

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Re: Lario ?
« Reply #23 on: December 01, 2019, 07:13:27 PM »
Welded valves have been the norm in many engine makers for years , good old high speed spin welding to attach stem to head ( hence different magnetic properties)
Have no idea about the Lario engine , but , if it's relevant I've had very good luck and longevity from Kibblewhite valves in my Le Mans 2.
I had no idea that model had such a checked history . Peter

Yes welded 2 piece, a complete red herring imho
Much on here a few years ago about this, kw being the (exy) valves of choice
Irrelevant now, new oe valves are definitely up to task, exhaust is actually one piece austenitic ss like kw or other aftermarket
Inlet is 2 piece ferrous but not an issue
More important is possibly hard tips negating the lash cap stuff

Again only mho but all the wear on valve tips, adjusters, pushrods, cams and followers were SYMPTOMS of the same issue.

Golario
Look closely at valve tip where it meets rocker adjuster, all Iíve seen (even with lash caps) show the problem
Actually not one of 20 valves I removed would even leave the building without grinding the tip
A rock and a hard place, who wins ?
Measure valve travel with new cam installed and spring pressure at said travel, was infinite on the only oe head I had, all over the shop on the modified ones. Phil tells you clearly how to measure.
Install new springs with correct preload, check for clearance everywhere, forget anybodies opinions, including mine
Measure 3 times, cut once, price for failure is high, fixed they are great
Fixing a symptom Is never the answer

Offline GoLario

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Re: Lario ?
« Reply #24 on: December 02, 2019, 12:56:51 PM »
Hello,
@moto-uno, @jacksonracingcomau,
Thank you very much for your help
I agree that unfortunately a lot of things observed and discussed are symptoms,
the consequences, of the circumstance that pushes the Lario into the danger zone
Therefore allow me to push things a bit further and please bear with me
Let us concentrate on the exhaust valves
Case 1:
Assume the exhaust valves in my Lario are 2-piece welded valves
That might explain why the valve stem has a strong magnetic response and the valve head a much weaker response
BUT, here we go, WHY is the magnetic response in the center of the valve head considerably weaker than at
the periphery of the valve heads ?

Case 2:
Assume the exhaust valves in my Lario are one-piece valves
Then of course we have to explain WHY the magnetic responses in valve stem and valve head are different AND WHY the difference
between center and periphery of the valve heads exists

Either way we need an explanation
With a lot of hesitation, as I might tell utter nonsense, I am tempted to believe that the issue here is TEMPERATURE
The highest temperatures are in the center of the valve head and in a section of the valve stem close to the valve head
In my Lario, and all other Lario's, these temperatures are on a level that allow for a rearrangement of
the crystalline structure of the used material(s), degrading its toughness, resulting in valves inferior for their application
My Lario is, as all Lario's, on its way to a "valve drop", but we are lucky we can have these observations before that happened

Do I have to apologize for what is utter nonsense or do we have a possible clue here ?

Thank you for patience
Kind regards,

Evert

Offline Chuck in Indiana

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Re: Lario ?
« Reply #25 on: December 02, 2019, 04:53:17 PM »
Quote
Do I have to apologize for what is utter nonsense or do we have a possible clue here ?

Certainly no apologies needed. When I was working in heat treat in the tool room, I had to be careful to make sure the pieces being hardened were north/south when they went into the quench or they would warp. Magnetic properties definitely change at austenitic temperatures. Does this have anything to do with the small block valves? Dunno.  :smiley:
Chuck in (Elwood) Indiana/sometimes SoCal

02 Scura RC
87 AeroLario
79 G5
95 Skorpion tour
 
I think senility is going to be a fairly smooth transition for me..

Offline GoLario

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Re: Lario ?
« Reply #26 on: December 04, 2019, 01:15:31 AM »
Hello @Chuck,

Thank you for your reply
I would love to find the answers to the "dunno" in your reply
In the 2-valve SB's, the components used and their materials specifications were doing a
reasonable job, although there might have been room for improvement
In my view the same components and the same material specifications were used for the 4-valve engines
BUT, the 4-valve engines were designed to breath better, deliver more combustion heat, being revved higher
The temperatures and the temperature gradients, in and around the exhaust valves, will be higher in the 4-valve
As the the effect of the temperature / temperature gradients is not linear (?), the impact on the material properties of (the valves)
could be dramatic, and even result in a rearrangement of the crystalline roster of the material
If that happens the thermal stresses will become the dominant factor and quickly, unpredictably destroy the valve and the engine

What do you think, worth to explore this a bit further or dump this line of thinking ?

Kind Regards,

Evert


Offline OKA

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Re: Lario ?
« Reply #27 on: December 04, 2019, 05:22:25 AM »
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


Online Kiwi_Roy

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Re: Lario ?
« Reply #28 on: December 04, 2019, 09:25:39 AM »
I remember seeing a Lario at the John Day National a few years back.
The owner had scrapped the 4 valve heads and fitted some 2 valve ones V65 I think

I owned a Lario for a couple of years but never got attached to it because of the plastic and the silly spring loaded side stand.
It became a bit tappy at one time, I pulled the valve cover off and one of the tappets fell on the ground, just put it back in and it was fine.
Last I heard it was back over on Vancouver Island.
72 Eldorado
07 Griso 1100
17 V7iii Special

Moto Guzzi - making electricians out of riders since March 15 1921

Offline GoLario

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Re: Lario ?
« Reply #29 on: December 04, 2019, 12:15:54 PM »
Hello guys,

Many thanks for all this feedback

@OKA,
how many kilometers did the engine do ? This for future comparison when mine has been stripped
Where all 4 lobes on the cam / tappets shattered ?
Do you still have the valves?
Is it possible to carefully investigate them ?
It would be fantastic if we could compare our findings; two engines that did not YET lost a valve !

I have no problem accepting your explanation and all taken measures make sense
You found the very evidence for this sequence of events, eventually leading to valve-drop, if no other fatal damage comes first
BUT, the consequence is that we should ALWAYS see a shattered cam / follower when we have a "valve-drop"
From the information around and I was able to find, that seems NOT (always) to be the case
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
So, is there room for another sequence of events leading to the valve-drop ?
Then we would have two processes for destruction present
And it would depend on the operating boundary conditions for the engine,which one becomes the dominant process, resulting in a valve-drop
As a valve is ALWAYS subject to mechanical / tensile stresses AND thermal stresses, I am so keen on exploring the effects of the latter one
For example, a common reason for stretched valves is a mismatch between specified material properties and operating temperatures 
Does this makes sense ?

With regards to the oil restrictions:
In my engine they are 2mm diameter
I believe a knowledgeable member, IceBlue, mentioned they are ex factory 1 mm ?
The oil supply should of course suffice the lubricating requirements
Any supply in excess will cool down the engine components, lowering particularly the temperatures in the valve stems !
How much is realistic and possible I do not now (3mm over 2mm has an effect 9 over 4!)

I do hope we can continue our exchange of thoughts and will be able to compare things as we go

Kind Regards,

Evert

 

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