Why did Larios drop valves ?

[jacksonracingcomau]

Mine will go together soon
Any sage advise wecome.

[guzzisteve]

The ones I fixed were from over revving. Valve heads would then come off stem. Some had cam problems. It's all been documented here if you search around. Some interesting reads for sure.

[Muzz]

Martin, I suggest you send a pm to Iceblue.  Brian has a lot of experience with the 4 valve engine and has done a lot of research on it.

From what I remember, the problems came from the two piece valve stretching causing the head to fall off. Cause(s) amongst other things were the valve springs were too strong and something about the cam needing to be 14mm instead of 12.  I think he got valves made but I have heard that there is a Nissan valve that works, and also a Suzuki 250 valve. People have just used the outer only on the spring.

[pete roper]

IN my experience, which was a long time ago and not encyclopaedic, the two major causes were the overly heavy valve springs, (They just doubled up on the same springs as they used with the 2 valves but the stems were much weedier. Wasn't aware until recently of the two part nature of the valves.) this may alsoof been a contributor to the cam and tappet problems. The other one was heat dissipation. The finning on all the early smallblocks was always marginal and if the heads were allowed to get dirty so their ability to dissipate heat was impaired they would always tend to shed valve heads or in the case of Monzas and V65's crack heads between the seats and the plug 'ole. The Larios were even more grossly under finned so heat dispersion became even more of an issue. As for the 750 versions, (Shudder!) they were truly the acme of awful.

If you haven't already I suggest you call Mario at Thunderbikes. He used to race one I believe and was I think the author of the Suzuki GN 250 valve and spring fix.

[Gliderjohn]

Or you can do what Chuck In Indiana did and adapt a genuine MG 750 4V aero drone motor.



GliderJohn

[jacksonracingcomau]

Thanks all
Have read and heard loads but no definitive answer, all I have heard except very few now keep revs below 8. This would be one answer.
The few have given them grief, one a 750 cc factory dakar bike, raced in the proper heat, still going strong and fast.
Another a road race bike set up with special cam very modified heads. Very fast. But long gone, possible I find it one day but not likely soon

I have the later std cam just back from being lightly cleaned up by Phil Joy in UK, gave followers a tickle up too. May dlc them in aus, mob in geelong does that.
KTM elephant feet adjusters on shopping list
Yet to decide on valves and springs, but my one had lighter suzuki ones, definitely too light for job.
I only want factory performsnce for now, detuning it not really the answer or question.

May be as simple as inadequate valves but fact that 750 road bikes still did it after years of factory mods makes that unlikely. They never sold fixed afaik
But rfactory race bikes didn't drop valves, they broke other bits but not valves. In desert heat, pulling through sand.

May have to look inside the dakar bike

Next question
Why did the flat tappet recent 8v wear out cams and has anyone fixed that without resorting to rollers ?
I realise thay don't drop valves but the cam wear is the common ground
Rare as RHS s on 2v bb and high cam belt 4v afaik
Sb 4v definitely had camshaft issues, intriguing part is new v85 has gone to roller tappets like the bb 8v.
There is an answer here somewhere

[pete roper]

The 8V's don't wear out cams.

[kevdog3019]

Third world parts for the internals did not help the Larios. There’s lots of speculations and fixing symptoms seems to be what most do. Someone went with Nissan valves (Brian??) and I went with Kibblewhite valves/springs, et al. I DLC my Cam also for good measure. If heat is a problem I’m running a venerable sweat-box with mine. Pulling 15+% more hp with major head work, bigger valves, racing cam, much more fuel. Nobody dropping valves with solid parts, but nobody using solid parts either. Use a band aide and take your chances. The stock valves are shite. My 2 pennies.

[Rough Edge racing]

 How much spring pressure is too much, measured on or off the seat? 

[kevdog3019]

How much spring pressure is too much, measured on or off the seat?

Depends on your valves. For high revs and solid valves stock is about right according to Milich and a German dude Martin. I wouldn’t do it on stick valves. What does that tell ya’?

[kevdog3019]

I don’t disagree with what anyone has said about the Lario flaws. My mentality is simply why live in a glass house. Prove to me with proper metallurgy and engineered parts that there are valves dropping. We simply don’t have that data

[Rough Edge racing]

Depends on your valves. For high revs and solid valves stock is about right according to Milich and a German dude Martin. I wouldn�t do it on stick valves. What does that tell ya�?

 I'm looking for actual installed PSI to make a comparison to other known examples...

[huub]

i've had two lario engines drop valves,  current setup is stock valves with soft springs , and a 8500 rpm rev limiter
it seems to keep together for now.
basically the 4 valve engines were not properly engineered, using valve springs from the 2 valve engine ( why?) the cam and followers wear out pretty fast.
when the cam is damaged the quitening ramps wear out, and the valves are violently opened. wich doesnt help the already fragile valve train.
the V35 imola2 suffers even more from dropped valves , because it revs higher .

[ossaman55]

I'm currently building a lario also and have been told by a friend that races them that the quality of the original valves and the soft cam and followers are the culprit. Replace the valves with kibblewhite stainless valves and dlc coat the cam and followers and it should never have a problem. Changing the valve springs to a softer spring drops redline and can cause valve float at the upper rpm range.

Sent from my moto x4 using Tapatalk

[kevdog3019]

I'm currently building a lario also and have been told by a friend that races them that the quality of the original valves and the soft cam and followers are the culprit. Replace the valves with kibblewhite stainless valves and dlc coat the cam and followers and it should never have a problem. Changing the valve springs to a softer spring drops redline and can cause valve float at the upper rpm range.

Sent from my moto x4 using Tapatalk

Amen brother

[wrbix]

Kevdog and Ossaman - been awhile ago but when looking at the Kibblewhite site there was no cross reference to valves for the Lario and email contact was likewise not helpful.
Got Kibblewhite part numbers?
or were your valves bespoke?

[kevdog3019]

Kevdog and Ossaman - been awhile ago but when looking at the Kibblewhite site there was no cross reference to valves for the Lario and email contact was likewise not helpful.
Got Kibblewhite part numbers?
or were your valves bespoke?

Mine are not stock. I had heads milled and using larger valves than stock. Maybe Ossaman can help here.

[ossaman55]

I actually haven't assembled my heads yet but I bought new lario valves from Stein dinse before I gathered all the info I have now. I believe that you need to measure your valves and order blanks from kibblewhite and have them cut to length and the keeper groove cut in. I wish I would have gone this route but I'm going to try the Stein dinse valves for now and keep a very close eye on them.

Sent from my moto x4 using Tapatalk

[huub]

not sure you need the stiff original valve springs , the valves are lighter, the rockers heavier but there are two sets of springs operating one rocker.
the original lario valves were made from some steel , and were magnetic current guzzi valves are stainless, only the hardened tip at the top is magnetic

i started collecting parts to build a spare engine ,
latest find is a set of 86 mm pistons and cylinders for a lario,
never seen those before
some pistons from left to right : 86 bigbore for lario, stock lario, imola 2 bigbore, v35 imola2

[jacksonracingcomau]

The 8V's don't wear out cams.

Actually Lario problem is similar to BB 8v one, it is the flat tappets that wear.   cam follows,
Factory sells / gives cams in kit for a reason
Any 8v BB 's been ridden for long after tapets worn ? Look at cam


But agree with all above, good valves and cam/followers dlc'd should fix issue
Spring pressure will be measured and springs bought
But I do want mine to see 9 without collision
KTM elephants foot adjusters may be blind alley but looking good to me right now, anything that makes valve train easier has to halp.

[pete roper]

Actually Lario problem is similar to BB 8v one, it is the flat tappets that wear.   cam follows,
Factory sells / gives cams in kit for a reason
Any 8v BB 's been ridden for long after tapets worn ? Look at cam

No, the problem is completely dissimilar. Using that logic is like pulling the head off a Lario that has dropped a valve and seeing a smashed up piston and saying "Gee Whizz! Larios have a problem with their pistons!"

The reason cams are part of the kit are twofold. Yes there is usually some compromise to the cam but the real reason is that flat and roller tappet profiles are completely different.

The thing that kills 8V big block tappets is I believe related to the beehive springs. Despite being chosen specifically to combat surge at certain speeds some form of occilatory effect occurs which allows the tappet to leave the opening flank of the cam.

If you look at the nose circle of the cams they will show a noticeable 'Bullseye' pattern, it's almost like a tempering mark which is unsurprising because that is exactly what it is.

The nose circle is NOT the point of highest load on the cam, in fact the loadings  that point are quite low. The point of highest load is at the base of the opening flank where the cam in not only being asked to overcome spring pressure but also accelerate the mass of the valvetrain.

At a certain point though the engine speed will coincide with the surge issue in the spring, the tappet will leave the cam and then slam down on the nose circle. Because the DLC coating is only microns thick and is also very frangible it will crack and craze, (This can be seen with the naked eye as a changing of hue of the coating but can be very clearly seen with images made with an electron microscope.).

When at rest and assisted by the the fact that the 8V runs very cool a lot of moisture will tend to accumulate in the rocker covers and then drips down into the cam weirs and onto the tappets. This will penetrate the cracks in the DLC and attack the parent metal of the tappet. After some indeterminate number of cycles when the engine is started again the sweeping action of the cam across the tappet will begin to abrade the lifting coating and the tappet fails. This is why failures seem on the whole to occur earlier in cooler, damper, climates.

The 'Bullseye' effect on the nose circles is due to the hammering caused by the descending tappet, it's a simple witness mark but by the time the cams are seriously compromised by the damaged tappet it is easy to see that the abrasion begins on the opening flank, not the nose, of the lobe.

In my experience, which as I've said is not nearly as extensive with the smallblock 8V the wear patterns on both cam and tappet are far more traditionally indicative of too heavy springs exerting too great a load on cam and tappet faces. The heavy seating load imparted by the springs must also be murder on the necks of the very thin stemmed 4V valves. It's a recipe for wiped cams and torn off valve heads and, surprise, surprise! That's just what happens.

Pete

[jacksonracingcomau]

No, the problem is completely dissimilar. Using that logic is like pulling the head off a Lario that has dropped a valve and seeing a smashed up piston and saying "Gee Whizz! Larios have a problem with their pistons!"

The reason cams are part of the kit are twofold. Yes there is usually some compromise to the cam but the real reason is that flat and roller tappet profiles are completely different.

The thing that kills 8V big block tappets is I believe related to the beehive springs. Despite being chosen specifically to combat surge at certain speeds some form of occilatory effect occurs which allows the tappet to leave the opening flank of the cam.

If you look at the nose circle of the cams they will show a noticeable 'Bullseye' pattern, it's almost like a tempering mark which is unsurprising because that is exactly what it is.

The nose circle is NOT the point of highest load on the cam, in fact the loadings  that point are quite low. The point of highest load is at the base of the opening flank where the cam in not only being asked to overcome spring pressure but also accelerate the mass of the valvetrain.

At a certain point though the engine speed will coincide with the surge issue in the spring, the tappet will leave the cam and then slam down on the nose circle. Because the DLC coating is only microns thick and is also very frangible it will crack and craze, (This can be seen with the naked eye as a changing of hue of the coating but can be very clearly seen with images made with an electron microscope.).

When at rest and assisted by the the fact that the 8V runs very cool a lot of moisture will tend to accumulate in the rocker covers and then drips down into the cam weirs and onto the tappets. This will penetrate the cracks in the DLC and attack the parent metal of the tappet. After some indeterminate number of cycles when the engine is started again the sweeping action of the cam across the tappet will begin to abrade the lifting coating and the tappet fails. This is why failures seem on the whole to occur earlier in cooler, damper, climates.

The 'Bullseye' effect on the nose circles is due to the hammering caused by the descending tappet, it's a simple witness mark but by the time the cams are seriously compromised by the damaged tappet it is easy to see that the abrasion begins on the opening flank, not the nose, of the lobe.

In my experience, which as I've said is not nearly as extensive with the smallblock 8V the wear patterns on both cam and tappet are far more traditionally indicative of too heavy springs exerting too great a load on cam and tappet faces. The heavy seating load imparted by the springs must also be murder on the necks of the very thin stemmed 4V valves. It's a recipe for wiped cams and torn off valve heads and, surprise, surprise! That's just what happens.

Pete

Yeah springs are the common culprit in most opinions
In both cases changing the spring would have been easy fix if it was case.
But my lario engine, fixed by guru with suzuki springs both dropped a valve and destroyed follwers.
Cam worn beyond use
Of course it worked for lady owner before me, only using some revs did it fail, actually less than 7500 when it popped, but cam wear had obviously already happened.
Correct seat pressure loaded and not are obviously important, but underlying issue is greater than that.

not sure you need the stiff original valve springs , the valves are lighter, the rockers heavier but there are two sets of springs operating one rocker.
the original lario valves were made from some steel , and were magnetic current guzzi valves are stainless, only the hardened tip at the top is magnetic

Thanks, that makes sense, they obviously have tried, posthumously it seems

I don’t disagree with what anyone has said about the Lario flaws. My mentality is simply why live in a glass house. Prove to me with proper metallurgy and engineered parts that there are valves dropping. We simply don’t have that data

Yours one of few that have been built to rev
What sustained revs are you happy pulling ?
How many miles so far ?

ATM I'm still trying to find out fatory fix for dakar bikes, have a lead on factory engineer at time, will post here if I get answer, might be a while.
Now I'm getting obsessed, it is a disease

If I can get std one to hold together, next one will make some grunt, potential is there for sure but I need to make sure the pin has been deactivated before I throw too much explosive in the grenade.

[huub]

Actually Lario problem is similar to BB 8v one, it is the flat tappets that wear.   cam follows,
Factory sells / gives cams in kit for a reason
Any 8v BB 's been ridden for long after tapets worn ? Look at cam


But agree with all above, good valves and cam/followers dlc'd should fix issue
Spring pressure will be measured and springs bought
But I do want mine to see 9 without collision

all the lario/ v75 dyno results i have seen have the max power at around 7000 RPM, and it hangs on to power up to 8000.
after 8000 power drops off sharply
no use revving it higher, it will be making less power.
if you want more revs, you will need at least a hot camshaft and bigger carbs.

[jacksonracingcomau]

all the lario/ v75 dyno results i have seen have the max power at around 7000 RPM, and it hangs on to power up to 8000.
after 8000 power drops off sharply
no use revving it higher, it will be making less power.
if you want more revs, you will need at least a hot camshaft and bigger carbs.

Thanks again, bigger carbs def on next but this one won't do much more than std. Vaglia tach only a rough guide, Don't need a dyno but a decent tacho will at least give me a referece point.
Factory claimed peak at 7800, others have claimed 8500. A little overev before it goes pop would be nice, also preps it for building faster one next.
Mate who raced very modified one in 90's had safe 10, but race bikes don't do big miles so longevity of camshaft & followers was prob never really tested. As you said before, that is definately a major part of the problem. Intend to prove fixed before anything else.

[huub]

from a well developed v75 from a club member, some head work,  pod filters and open exhaust

[jacksonracingcomau]

from a well developed v75 from a club member, some head work,  pod filters and open exhaust

How long has that held together ? Miles ?
Mine will be a 650 for now, might go a few more rpm. But if it does similar safe for 10000 miles I'd be happy. On the noise, of course.
Take it that has ligher valve springs than stock ? Same late sb 2 valve springs Iseblue uses ?

[jacksonracingcomau]

Ok I am back in oz with chuck's lario, my one that dropped valve and one 750 4 valve head with rockers.
Mine and chucks have cam worn to nothing, every valve stem, pushrod, rocker adjuster hammered.
Guess his was seconds from going pop
Both these two had light valve springs
Intriguiong one is 750 head, this would have had later cam, but valves and rocker adjusters are chewed out just like the other two. But valve springs I think are original, certainly much heavier than the other two.
Dummied a motor up with carb springs for valve springs just to measure clearance, with nearly new OE 14mm cam, have loads of valve-valve but inlet valve to piston is 0.050"
WITH CHUCK's aero cam that becomes 0.030" def not enough.

So tell me Lario people, anyone with late 14mm cam, do rocker adjusters and valves still take a hammering ?
Easy enough to fit lash caps and hard adjusters but symptom and cause getting to me here.
Very tempting to assemble with piston fly cut for clearance but still feel there is another underlying problem.
Am all ears

[huub]

all the four valve engines i stripped had worn camshafts.
in my opinion cams and followers on a lario are marginal at best.
the valve train just wasnt designed to open two valves with one cam.


i want to try having the camshaft DLC coated.

smallblock adjusters wear out pretty fast , some people use yamaha adjusters.
the rest of the valve train should be OK , if you use good valves and spings

[jacksonracingcomau]

all the four valve engines i stripped had worn camshafts.
in my opinion cams and followers on a lario are marginal at best.
the valve train just wasnt designed to open two valves with one cam.


i want to try having the camshaft DLC coated.

smallblock adjusters wear out pretty fast , some people use yamaha adjusters.
the rest of the valve train should be OK , if you use good valves and spings

Thx
So 14mm cams wear out same as 12mm?
Adjusters wearing is possibly symptom of cam worn out.

[Simmoto]

I agree with much of what's been said.

I reckon poor materials is a big part of the problem with the cam (12 and 14mm) not so much the design. What are the cam and followers made of? If poor quality steel is the problem has anyone thought about having a cam and followers made?

This is what I'm thinking - pull the stock 12mm cam and followers as a pattern and have a chilled iron (or other durable material) cam and followers made by a specialist. Add to my existing one piece stainless valves w/lash caps.

My machine has stainless steel one piece valves with machine matched guides and Suzuki GN250 springs. Might change the springs if I upgraded the cam and followers.

Would this work or would it trash the pushrods or some other component?

Whadya think 

Cheers