From Valves to Rocker Arms "98 V11EV

[n3303j]

So my valve issues are reasonably resolved at this point. Right down to the fact that it is not uncommon to grind material off a valve stem to compensate for valve and seat reworking setting the valve deeper in the head.

So I took a hard look at my rocker arm tips where they contact the valve stem. They are worn and have changed profile from a smooth radius to a slightly roughened and worn contour.



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More importantly it appears that the tips are case hardened and the wear area has gone through the case. So the valves are now being actuated by a soft and rough metal arm. I assume this puts a bit more side load on the valve stem during each actuation. I'm surprised the arms wore through the case hardening in 80K miles.

Replacement arms are about $160 each. Anyone out there rebuilding and regrinding rocker tips?

[guzzisteve]

Go roller rockers, much gooder. For the price of fix or new you can get rollers.

[guzzista]

Ducati 748/916/996 had rocker wear issues. Check with  shops  that were refurbishing  them

[pressureangle]

Baisley can fix your old rockers or convert them to roller as I did for my LM1000. The roller conversion is heavy and needs heavier valve springs to go with.

http://www.baisley.com/rocker_service.htm

[bigbikerrick]

What is the cause of that type of wear, poor metallurgy, oil with insufficient ZDDP, excessively loose valves, or any other cause?
Rick.

[Frenchfrog]

At what price would roller rockers come at then ?
Horrifically expensive I guess.

[n3303j]

At what price would roller rockers come at then ?
Horrifically expensive I guess.

$450+ according to their website. Then there's the issue of needing heavier springs and overloading tappets and cam. I'm supposing it's metallurgy. As the tappes and cam are perfect and so must have enough ZDDP.

[Frenchfrog]

Not quite as "ouch" as I would have thought then...still a fair amount of coin though.The old school answer in the UK ,if badly worn, would be to get some stellite welded on and grind that back to the original profile.I'm certain that you could find some one in the US to do that and it shouldn't be very expensive at all.

[fotoguzzi]

My rockers with 94k do not show much wear at all.

[n3303j]

I was hoping for a name of the welder. Ed Korn used to do lifter faces for /2s but he stepped out of it for other ventures.

Don't know what you define as "little wear".  Mine have little wear, but enough that it's penetrated the case hardening.

[Chuck in Indiana]

Just MHO, but if it's penetrated the case hardening, that's a *lot* of wear.

[n3303j]

Just MHO, but if it's penetrated the case hardening, that's a *lot* of wear.

I agree, but a case hardening can be 0.002" so it doesn't seem like a lot.

Evidently it wasn't a sufficient depth for the application.

[chuck peterson]

I’ve seen the same. Sold the perfectly running bike 30k miles later, fool that I am. Look again after your next oil change. See if anything is different. Compensate the gap a touch? Any idea of its early oil life? Are newer oils of today keeping it from getting worse? Oil filter or no? What’s a rocker cost these days? Could it be Guzzi just figured it would be replaced during an overhaul..i did have a machinist say they could not be ground to a smooth radius, it would expose all of it to wear on the untreated metal..I’ve wondered if there is still enough there to maintain it just as is…? Built in resilience

[n3303j]

Welding tip and regrinding profile would be only acceptable repair. Stellite probably okay if it would create a stress free bond. Just a regrind would break through the case and leave you with a soft rocker tip.

Oil is filtered. What surprises me is that all four cam lobes and four lifters are all perfect without a mark. They get a lot more shear wear than a valve end / rocker interface.. I guess it's just a poor choice of materials and heat treatment at the rocker / valve interface.

[bigbikerrick]

How about finding a used set of rocker arms in good shape,and just replace them?  It seems that would be the best, most cost effective solution. They have to be a few "junk" square head big blocks somewhere for parts.
Rick

[Chuck in Indiana]

I agree, but a case hardening can be 0.002" so it doesn't seem like a lot.

Evidently it wasn't a sufficient depth for the application.

I've never heard of that little thickness of case hardening. .020 would be more like it in my experience.

[Mike Tashjian]

Yes, the hardening should be deeper than .002.  I read an article about a guy who made a jig to hold his rockers so he could grind the radius.  It wasn't that hard to do and his results were very good.  I forget what small car it was but the rockers were expensive and otherwise in good condition. 

[n3303j]

Quote: "Cyanide hardening produces a shallow hardness layer of . 5 to 5 mils in depth with a hardness of 50 to 65 HRC."

Cyanide hardening is relatively common where depth isn't required.

[n3303j]

How about finding a used set of rocker arms in good shape,and just replace them?  It seems that would be the best, most cost effective solution. They have to be a few "junk" square head big blocks somewhere for parts.
Rick

Went through eBay and found a suitable set with 7K miles on them. $150 and that problem is now solved. Thank goodness Guzzi used the same part numbers over a large variety of engines. These were '89 Cali 3 1000.

[bigbikerrick]

Went through eBay and found a suitable set with 7K miles on them. $150 and that problem is now solved. Thank goodness Guzzi used the same part numbers over a large variety of engines. These were '89 Cali 3 1000.

                                                                                                                 

                                                                                                                     

[Mike Tashjian]

What makes you think they are Cyanide treated?  Case hardening is always what I see. I never saw a wear part specified for cyanide treatment in any shop I worked in.  Nice you found some used parts.  I would be curious about your old ones.  I would probably regrind the radius and see if they are still hard after they clean up. 

[n3303j]

What makes you think they are Cyanide treated?  Case hardening is always what I see. I never saw a wear part specified for cyanide treatment in any shop I worked in.  Nice you found some used parts.  I would be curious about your old ones.  I would probably regrind the radius and see if they are still hard after they clean up.

No idea if the rockers are cyanide treated. I only mentioned cyanide hardening as a case hardening process because someone said they thought case hardening was 0.020" deep average. Boiling low carbon steel in a red hot cauldron of cyanide was a way to add carbon to the surface of low carbon steel and harden that surface. It was very shallow hardening but could serve as a sufficient wear surface in some applications. It also increases strength, toughness and dimensional stability.

I feel a shallow case would not be suitable for rocker tips as they are a small area under heavy shear loads. My four rockers all show a wear pattern typical of penetrating a hard case and abrading on the soft material below. Regrinding the tips would put the whole surface into the soft appearing core and would probably wear very rapidly.

That's why I was hoping there was someone who welded the tips with stellite (or similar) and then reground the tips. Ed Korn used to weld tappet faces that had surface failures and regrind them (BMW). But he has headed in another direction.

But at the $150 for 4 rockers from a 7K mile bike I think I got out the cheapest way possible (Guzzi Content) that will give me durable results.

[Chuck in Indiana]

One of the many hats I've worn over the years is tool room tool hardener. I know a little about it.
as Mike said,

I never saw a wear part specified for cyanide treatment in any shop I worked in. 

He speaks truth. 

[n3303j]

One of the many hats I've worn over the years is tool room tool hardener. I know a little about it.
as Mike said,He speaks truth. 

Journeyman tool & die maker here.
As a kid in my father's shop I used to get to make some of the runs to New Britain (Connecticut) Heat Treat. I'd get to wander around the place (before OSHA) and see stuff in process. One of the interesting areas was crucibles filled with red hot Sodium Cyanide with steel parts submerged in the Cyanide. Looked like miniature versions of what I was told Hell would be if I didn't straighten up and fly right.
https://youtu.be/6yiF7TenTeE  See around 3:30.
Or Google "cyanide case hardening".
Just because you haven't seen it doesn't mean it doesn't exist.

https://rupertharris.com/products/cyanide_hardening

[chuck peterson]

So we see this on rockers… but how come we don’t see/hear stories about them self destructing all the way thru the hardening and puking metal into tiny specks thru out the motor?

Anyone seen one totally destroyed? Just asking..
Where is the evidence that things get worse then what we see here..

Inquiring minds want to know..

[n3303j]

So we see this on rockers… but how come we don’t see/hear stories about them self destructing all the way thru the hardening and puking metal into tiny specks thru out the motor?

Anyone seen one totally destroyed? Just asking..
Where is the evidence that things get worse then what we see here..

Inquiring minds want to know..

I don't think the failure is catastrophic. It's more a loss of durability. When a rocker pushes a valve the tip of the rocker is traveling in an arc. The valve stem travels in a straight line. Therefore, as the valve opens the rocket tip is sliding across the end of the valve stem. There are a number of articles that discuss centering this "wipe pattern" on the end of the valve stem to minimize side loading of the valve.

Now if the rocker tip surface deteriorates (like in my photo) it will add friction as it wipes the top of the stem. This translates to more rapid valve guide wear in the direction of the wipe. So you got 80K out of a factory engine and now you might only get 50K out of a rebuild by ignoring all the details that contribute to longevity.

But back to the real world, there's no reason that the rockers should wear through the case on their tips in 80K miles. I'm assuming I got a bad batch. Heck, if BMW can make heads that progressively deform in service I'm sure Guzzi can make (buy?) rockers that aren't suitable for long term service.

[pressureangle]

That's why I was hoping there was someone who welded the tips with stellite (or similar) and then reground the tips. Ed Korn used to weld tappet faces that had surface failures and regrind them (BMW). But he has headed in another direction.

But at the $150 for 4 rockers from a 7K mile bike I think I got out the cheapest way possible (Guzzi Content) that will give me durable results.

If you missed it above, Baisley does hardface and regrind stock rockers. I'm pretty sure it would be more expensive than simply having found good used stockers.

[n3303j]

Thanks. 7K mile rockers from eBay arrived today. $150. Condition excellent! Got off cheaply (the Guzzi way).

[Tom H]

I don't think the failure is catastrophic. It's more a loss of durability. When a rocker pushes a valve the tip of the rocker is traveling in an arc. The valve stem travels in a straight line. Therefore, as the valve opens the rocket tip is sliding across the end of the valve stem. There are a number of articles that discuss centering this "wipe pattern" on the end of the valve stem to minimize side loading of the valve.

On the centering: My '73 R75/5 states to offset the rocker on the valve to promote spinning the valve. This would keep valve stem wear more even. In general, cams to solid lifters are sometimes offset to spin the solid lifter. May apply to hydraulic lifters as well.

Wipe?: I guess you could call it that. When I have worked on my Guzzi heads, there "appears" to be a thin divot line, like the rocker hits that rocker contact area size spot and does the push. Maybe I have not looked close enough to see that it's not actually a thin straight line, but is actually a gradual sloping edge divot, "Wipe". I do know that when I worked in a machine shop helping with old V8 heads, we regularly ground the tips of the valves flat on a valve grinding machine as well as faced the head angle.

Not trying to give you a hard time, just pointing out that things are not always cast in stone.
Tom

[n3303j]

Tom,

On your BMW the valve stem keepers are full half circle and they butt to form a full circle. The circle diameter is ever slightly larger than the valve stem. Your valve stem probably has 3 grooves to give a greater surface area to wear as the valve rotates.

Moto Guzzi keepers are just shy of a half circle. So the pair does not butt when they drop into the top collar. Instead they clamp on to the valve stem and keep it stationary rotationally.

You do indeed get a line across the top of the where it is wiped by the tip of the rocker. The wiping action also wears the tip of the rocker.

Properly set up the tip of the rocker should wipe across equally both sides of center as it pushes the valve open. I smoothed the valve ends square and flat. I stoned the tip of the rocker to remove any uneven wear from 7K miles.

I did the installation and applied Prussian Blue to the valve ends and cycled the crank and valve train.  A subsequent examination showed that the rocker tip wiped a clean patch that was symmetric about the valve centerline. So I've got a perfect, flat contact patch on the valve stem. This rebuild should last as long as the original assembly.

https://www.lunatipower.com/how-to-verify-valvetrain-geometry
It's not a motorcycle engine but it illustrates the variations in contact patches produced by valvetrain geometry. On the BMW (/2) you would move the patch by shimming the rocker pylons.  Those butterheads frequently needed shimming. Don't remember having those problems with the '89 R100RS.