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Discussion Starter #1
Hi All!

I've been going through the forum, but cannot find a definite answer (or I'm searching with a wrong query:laugh:).
Thus, I've let myself open this thread. Namely:

The stock half-rings, that secure the valve, will change their shape (deform) while we put miles on the engine. I've read couple of posts where I found statements that deformed half-rings can influence the clearances. I even read that changing the used half-rings to new ones might 'reset the gaps' to the right spec (in some cases).

My questions are:
- How much influence can deformed half-rings have on the measurement/clearances?
- Has anyone measured what is the delta between the clearances on the shims (ie. when we install new stock half-rings and when we leave the old ones)?

Ceteris paribus, for the sake of this discussion I make the following assumptions:
- Bike is not used for trackdays
- We exclude situations where the half-rings are damaged
- Measurements can be easily reproduced in the same conditions

Cheers,
Paul.
 

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I often see about .001-.002" variance with new to used 1/2 rings. obviously it depends on how worn/ how loose the closing clearances were before measuring.

A loose closing clearance allows more movement and that equals more wear, I cannot give you a visual but at a certain point I do change non-broken 1/2 rings. most of the time these are caused by closing clearances that were left loose for too long and the 1/2 rings have been pounded. I never change 1/2 rings if possible because a set that are broken in and maintained are often good for the life of the bike. I have never changed them in any of my bike and do not suffer broken rings even when over reving motors, adjustments are due only to valve recession and not 1/2 ring wear for the most part.

It is not always easy with older eyes to read the 1/2 rings to make sure you do not put one in upside down, this is the best, maybe only benefit I see to the brickwood collets for most people. Yes putting a 1/2 ring in upside down has a similar effect to putting in new 1/2 rings. The collets are stronger but outside of a few race cams I have not seen much benefit, even those situations you are better off using taperlock collets but that is a rare case.

1/2 rings do not care if it is race or street use it is a matter of the cam profile (rapid or gentle ramps) and how loose closing clearances are. If you run a closer at .005" and run the bike at 1/2 max rpm you will likely see more deformation than a 1/2 ring run at .0005" going to full rpm. If you want to run loose closing clearances for whatever reason then yes the brickwoods may be a good choice for you.
 

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I've been running normal stock half-rings for the last 23 years on my bike, and they've been just fine. I assume that at some point in the last 25 or so valve checks they have been replaced; I don't know for sure. But they have never been a problem. After about 40K on the engine, everything was well settled in, and since then I generally have the valves checked once a year (usually between 11K and 17K miles) and they need some sort of adjustment about every two checks. I do the belts every two years.

PhilB
 
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I used to see about .002" change with new 1/2 rings. I only use my SS for track days, so the last time that I checked my valve clearances and found 2 broken 1/2 rings, I decided to switch to MBP collets. I love them. Haven't had to adjust valve clearances since.

Here's a picture of the broken 1/2 rings.
 

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Discussion Starter #6
Hi Gents,

thanks for all your answers!

It seems that the MBP collets from EMSDUC is the way to go - from what I read they can give you less headache :)
@ducvet: Thanks for the thorough explanation - it definitely adds more light to the 'magic' of setting up the valves. The little things always make the biggest difference - don't they?
 

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Discussion Starter #7
@Joe-B: The picture you attached gives me goosebumps! Truth to be told, out of 8 half-rings I dettached from my 900ss, only one was unbroken. The rest was total scrap.
 

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Odds are that if you put new 1/2 rings in you will still have loose closers, couple that with new 1/2 rings pounding in .001-.002" you have a recipe to break them again. If using new 1/2 rings be sure to set them at zero with no drag on the cam. Then get back in there in about 1000 miles to adjust the closers back to zero one last time and you should be good to go.
 

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Another cause for the closer clearances to loosen up is the deformation of the closer shim where the half rings sit. This is more of an issue with all the Ducati made closers before 07' (includes all the 8 mm shims) The material used in these shims was a fairly soft steel. I measured the hardness of these shims and found them to be in the mid 40's Rc. (Rc is a Rockwell scale used to quantify the surface hardness of metal, the higher the number the harder the surface) When the 1098 was introduced, Ducati changed the material of all their shims to a Bearing Steel that is through hardened to about Rc 58.

Since the contact area between the half ring and the closer shim is theoretically a line contact, the stresses during use are quite high causing deformation in both the shim and the half rings.

The shims I have made in the US are made from A2 Tool Steel and are hardened to around Rc 60-62, just a bit harder than Ducati OEM.

The MBP retainers are also made from A2 tool steel, so with the combination of the newer shim material and the MBP retainers, you get a minimum of deformation over time, increasing the valve adjustment intervals.

Mike
 

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The shims I have made in the US are made from A2 Tool Steel and are hardened to around Rc 60-62, just a bit harder than Ducati OEM.

The MBP retainers are also made from A2 tool steel, so with the combination of the newer shim material and the MBP retainers, you get a minimum of deformation over time, increasing the valve adjustment intervals.
Well I wasn't aware of the science behind it but I concur on the 'increasing the valve adjustment intervals' when using the MBP retainers/EMS shims combination. :)
 

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Not sure if there is ever a issue with things being too hard (brittle?) I have personnalty delivered a set of powdered brickwood collets to Guy about a decade ago. It was courtesy of a set of very built race heads and V2 cams that ate everything. normal 1/2 rings would go a weekend and the brickwoods lasted 3 weekends.
 

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Not sure if there is ever a issue with things being too hard (brittle?) I have personnalty delivered a set of powdered brickwood collets to Guy about a decade ago. It was courtesy of a set of very built race heads and V2 cams that ate everything. normal 1/2 rings would go a weekend and the brickwoods lasted 3 weekends.
A2 is one of the best impact resistant steel there is. At the extreme high range of hardness, it does become a bit more brittle, but the hardness spec used does not make them overly brittle.

Were the retainers that broke 8 mm or 7 mm? The 8 mm are a bit thinner due to physical constraints of the groove in the valve stem and the ID of the closer shim. The 7 mm are a bit thicker and stronger.

One thing I did a few years ago was to redesign them to minimize stress risers. There used to be a flange that protruded on the outside of the retainer. The large change in cross section caused the part to deform during heat treat, which could add internal stresses.

Some of my customers race Superbike spec bikes (old Desmoquattro's) in Australia and they all use the MBP retainers. They say they get a whole season out of them.

Looks like there are situations where the fatique resistance of the part is exceded. But overall they are much stronger than the half rings.

Mike
 

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Discussion Starter #13
Hi!

Thanks everyone for the massive help - the details always matter!
@ducatimike Impressive knowledge you have!

I will be definitely trying the MBP shims, retainers but for the Paso 750 I just bought.
 

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Just to clarify...
My personal opinion is the MBP retainers are often not needed but certainly do no harm as long as they are installed correctly. They can be a benefit on valve adjusts as you can not install them upside down so for a hobbyist it is simpler to do correctly. This comes into play more as our eyes make it harder to read wear patterns.

99% of people will never come into contact with the super aggressive cams that can damage them and trust me if you get a set you will know (non issue for most).

Oem 1/2 rings do work well for 90% of situations but should be set up properly, if you plan on running lose closing clearances due to cams or ease of not adjusting the valves I do think the MBP retainers would be a wise choice.
 
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