8V tappet poll

[jlburgess]

 

[ChuckH]

I have the factory supplied roller tappets in my engine.  The '12 Stelvio was built in Feb 2012, bought in June 2012.  It now has 32K miles on it and I just did the service work, including a valve clearance check.  All readings were where they should be -- '006" Intakes, '008" Exhausts.  The bike has been running great.

Ride safe out there.

[Wayne Orwig]

I have the factory supplied roller tappets in my engine.  The '12 Stelvio was built in Feb 2012, bought in June 2012.  It now has 32K miles on it and I just did the service work, including a valve clearance check.  All readings were where they should be -- '006" Intakes, '008" Exhausts.  The bike has been running great.

Ride safe out there.

With the roller tappets, do you see much change in clearances when you check them?

[boxermoose]

Just had mine inspected at 32k miles - 2012 Stelvio

No issue - but this is Houston so limited cold weather condensation


....now to go check my swing arm, luckily my son does NDE for a living

[MGrego]

Recently did the roller conversion on my 2012 Norge with 3500 miles.  The flat tappet surfaces showed the beginning of breakdown of the DLC.  I'll try to post a couple of pictures later --  I didn't really expect to see any breakdown of the DLC, but even with so few miles, it was starting to happen ....

[pebra]

Recently did the roller conversion on my 2012 Norge with 3500 miles.  The flat tappet surfaces showed the beginning of breakdown of the DLC.  I'll try to post a couple of pictures later --  I didn't really expect to see any breakdown of the DLC, but even with so few miles, it was starting to happen ....

Was anything covered by Piaggio?

I just talked to the importer about my 2009 Griso. If I  thought I had a case I'd have to provide them with documentation, any reimbursement of a roller tappet conversion would be considered case by case. No surprise about that.

[MGrego]

No. In my case, I purchased the bike used, with an unknown service history, and no warranty left.  I just decided to do the conversion on my dime --

[MotoG5]

I have the factory supplied roller tappets in my engine.  The '12 Stelvio was built in Feb 2012, bought in June 2012.  It now has 32K miles on it and I just did the service work, including a valve clearance check.  All readings were where they should be -- '006" Intakes, '008" Exhausts.  The bike has been running great.

Ride safe out there.

I thought that the roller tappet settings were .004" and .006".

[canuguzzi]

Factory rollers. Valves remain in spec for two adjustment periods.

[MGrego]

More information for the collective knowledge on the flat tappet issue:



2012 8V Norge tappets, 3500 miles

[ChuckH]

With the roller tappets, do you see much change in clearances when you check them? 

Wayne,
I check them regularly at 6K intervals, or a bit earlier if I'm ready to go out on a trip.  Oil and filter get changed at the same time.  I've got all of the records but, as I recall, the clearances have not changed, either up or down, more than .001" on any of the intervals.  This last check, just done this past week, was the only one where all readings were right where they were set.  Apparently, they finally seated in.

[ChuckH]

I thought that the roller tappet settings were .004" and .006". 

Moto,
I'm just going on what Jim B. at Rose Farms told me -- .006" Intakes, .008" Exhausts -- for the roller tappet 8V engines.

[Vasco DG]

The 8V bikes seem a bit strange in that the clearances open up appreciably as the engine heats up. I've experimented with going down to 2 and 4 and it still behaves itself when hot because whipping the cover off and checking them as quick as possible I was still finding them at five and eight when hot.

I suggest 4 & 6 for safety and quietness.

Pete

[mwrenn]

 

Recently did the roller conversion on my 2012 Norge with 3500 miles.  The flat tappet surfaces showed the beginning of breakdown of the DLC.  I'll try to post a couple of pictures later --  I didn't really expect to see any breakdown of the DLC, but even with so few miles, it was starting to happen ....

Does the factory DLC coat the tappets?  Another question, do you have any way to check the Rockwell hardness of the tappet face?

[Vasco DG]

Does the factory DLC coat the tappets?  Another question, do you have any way to check the Rockwell hardness of the tappet face?

No, but the Australian Mint does and that's where I got the original chilled cast iron tappets tested. They were, in some cases, not hard enough. You can't use a Beakers machine on DLC as its a penetrative test not a density test.

Pete

[mwrenn]

No, but the Australian Mint does and that's where I got the original chilled cast iron tappets tested. They were, in some cases, not hard enough. You can't use a Beakers machine on DLC as its a penetrative test not a density test.

Pete

Ok, thanks for the info.  I am working with some H13 hot work tool steel, making tappets for a project V7. Hardening to 50-51 Rockwell to match the factory hardness.  Following the tappet failure thread with great interest.

[Vasco DG]

Ok, thanks for the info.  I am working with some H13 hot work tool steel, making tappets for a project V7. Hardening to 50-51 Rockwell to match the factory hardness.  Following the tappet failure thread with great interest.

I've spent a lot of time communicating with people a lot cleverer and better educated than myself on this issue, as I often say I'm just a facilitator and communicator but I DO try and do the research. If people ask me at the time I can probably post links to some of the wordy and mainly tedious papers that have been written by boffins on these subjects but really it isn't probably worth it.

The gist of the matter though is there are problems getting DLC to adhere to a ferrous substrate and also because of its frangible nature flexing of that substrate during use may cause the coating to craze and shatter. This issue can be exacerbated by the use of incorrect lubricants or certain additives.

External environmental issues such as moisture, heat and incorrect servicing are another dead fish that has to be thrown into the mix. NO I don't have 'The Answers' but I'll bet you a bus full of beehives I've done a damn sight more research and testing on this issue than just about anyone else outside the factory. Does that mean my suppositions are right? No, but the scientific method requires that peer review disprove my findings rather than just being shouted at by blockheads who haven't got a clue and just want to pile on.

Pete

[molly]

I suppose it is possible the DLC just can't cope with the impact of the cam as it leaves and returns to the tappet.

http://www.sciencedirect.com/science/article/pii/S0043164810000505
The above is from Leicester university (UK) department of engineering.

I am losing the plot a bit here, was DLC applied after the intial failures?

[MotoG5]

I am losing the plot a bit here, was DLC applied after the intial failures?

That is my understanding. It was an attempt to fix the issues fist encountered. When it became apparent that it did not work the change over to rollers was quietly instituted. 

[Vasco DG]

The tappet material was changed and the DLC coating added. Early tappets were batched produced chilled cast iron, later ones are forged steel with DLC coating. Foot shape of tappet and possibly radiusing changed with the V2 tappets. I believe, although I've not managed to confirm, that the V1 tappets were radiused for spin whereas the V2, DLC coated tappets are flat but the cam profile is angled ever so slightly in section. NOTE. I say this is something I haven't been able to accurately confirm!

I don't think it is the fault of the DLC. I think it's a combination of issues one of which will be the fairly major stresses imposed on the tappets by the somewhat aggressive cam profiles. Interestingly though on the cams themselves the major manifestation of damage during early detected failure is on the nose circles of the cams, not on the ramps or opening flanks where you would expect them to be.

Pete

[molly]

O.k. I get that, DLC obviously didn't solve a problem that already existed and was probably a last ditch attempt prior to rollers.

So what makes the 8v tappet/cam  relationship on the 8v motor so different to other engines that it constantly wears hardened or DLC coated components.?

[Chuck in Indiana]

Ok, thanks for the info.  I am working with some H13 hot work tool steel, making tappets for a project V7. Hardening to 50-51 Rockwell to match the factory hardness.  Following the tappet failure thread with great interest.

Wow..that's not very hard. I would think they should be at least RC 56-58? Disclaimer.. I'm certainly *not* an engine designer, but I've heat treated a ton of tool steels. Probably more than that, actually..

[mwrenn]

Wow..that's not very hard. I would think they should be at least RC 56-58? Disclaimer.. I'm certainly *not* an engine designer, but I've heat treated a ton of tool steels. Probably more than that, actually..

Apologies in advance for the thread drift...
Tested two Lario tappets, both at 52 Rockwell.  Checked later model new Guzzi tappets, same value.
The H13 cool down is at 1000 degrees F.  I can go harder, but I'm trying to match the factory spec.
We will see how they hold up...

[Chuck in Indiana]

Apologies in advance for the thread drift...
Tested two Lario tappets, both at 52 Rockwell.  Checked later model new Guzzi tappets, same value.
The H13 cool down is at 1000 degrees F.  I can go harder, but I'm trying to match the factory spec.
We will see how they hold up...

Oh, I understand, I would too.. it just surprises me. I've never personally heat treated H13, so it may be a completely different animal. For wear, we used to shoot for RC 56. Back in the Pliocene, when Pete was first investigating cam failures, he was finding RC 45. Now, I *know* that isn't hard enough. That's spring hardness..
Ok, did a little research, and H13 seems to be a strange alloy *to me* for this application. It's generally used to make die cast molds. I thought it sounded familiar..and yes, it's a completely different animal. I would have thought they would use a shock and wear resistant alloy like S7 for something like cam and lifters. That needs to be around RC 56. <shrug>
Live and learn..

[canuguzzi]

Oh, I understand, I would too.. it just surprises me. I've never personally heat treated H13, so it may be a completely different animal. For wear, we used to shoot for RC 56. Back in the Pliocene, when Pete was first investigating cam failures, he was finding RC 45. Now, I *know* that isn't hard enough. That's spring hardness..
Ok, did a little research, and H13 seems to be a strange alloy *to me* for this application. It's generally used to make die cast molds. I thought it sounded familiar..and yes, it's a completely different animal. I would have thought they would use a shock and wear resistant alloy like S7 for something like cam and lifters. That needs to be around RC 56. <shrug>
Live and learn..

For the rest of us, would it be fair to say that it isn't just a matter of the DLC but the material the tappets are made from and that the flat design might work just fine were different materials used to make the tappets? Just for discussion of course.

[trophy900]

I'm normally just a lurker here. Enjoy the banter, but not much for communicating by type. Anyway, I have experience in tooling systems and precision tool making that gives me info that is pertinent here. The term "DLC" is really pretty generic. There are a bunch of coatings that would fit that description with different capabilities and hardness. In this application, it would be a "PVD" type coating that is applied at around 900 deg F (possibly lower depending on the coating system). The question I've had is just because the coating is gone, it doesn't necessarily mean the tappet is damaged - only that the coating didn't adhere, and that is a pretty normal failure mode. The problem usually is the cleanliness of the surface that it's applied to. So when the coating is gone, has anyone actually inspected the tappet surface for wear? Any good tool maker could indicate that surface and tell you with in tenths of a thousandths (for us imperial guys) whether that surface is scarred or not. Actually the cam could be done also with more effort. Has that ever been done? If not, I can do it if someone can provide the components.

For the record - mines got 24K miles on it and I check clearances twice a year whether it's time or not and haven't made an adjustment more than a thou / thou and a half ever.

Ride Safe,
Jeff

[Vasco DG]

Once the wear reaches a critical point it all goes very bad very quickly and the parent material of the tappet vanishes rapidly.

Pete

[Chuck in Indiana]

For the rest of us, would it be fair to say that it isn't just a matter of the DLC but the material the tappets are made from and that the flat design might work just fine were different materials used to make the tappets? Just for discussion of course.

Well, I've never designed an engine, but I have designed and built many machines. I wouldn't think of using a mold steel for something like a cam or cam follower. Maybe that is what is commonly used? *I don't know.* H 13 is a high chrome alloy, and would have good rust resistance. That is certainly important..

[mwrenn]

Well, I've never designed an engine, but I have designed and built many machines. I wouldn't think of using a mold steel for something like a cam or cam follower. Maybe that is what is commonly used? *I don't know.* H 13 is a high chrome alloy, and would have good rust resistance. That is certainly important..

I am still in the experiment stage.  Will PM you the details Chuck.  Using the H13 for the pushrods cups that are pressed into the lifter bodies so that shorter pushrods can be used.  It is the same hardness as the stock cups after heat treat, and has excellent wear resistance.

[molly]

Once the wear reaches a critical point it all goes very bad very quickly and the parent material of the tappet vanishes rapidly.

Pete

That's the downside to coatings, they are thin and once compromised game over. I'm sure Guzzi would have chosen materials in the original design which normally would have been expected to do the job, we have to give them some credit I suppose.
The puzzling thing for me is  besides not knowing why the excessive wear is taking place is that the factory did not pick it up in the development stage. They manufacture a limited number of engines so it is not as if they were distracted by numerous other engine projects. Unless it was a Aprilia design.
 I would love to be a local in the factory watering hole and after a few beers and a few loose tongues, getting the real low down on the matter.