Oil Consumption-This might be your problem too!

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L.A.B. said:
Doesn't matter as the rings slowly rotate and why 2-stroke rings are pegged.

Rotation of piston rings

Piston rings lead a much more active life than might be thought. While we usually imagine that they only reciprocate in a motion defined by the piston, they also rotate during service. Such rotation has been the subject of many experiments and studies over the years, but this is not simply a...
www.highpowermedia.com

Method for Measurement of Piston Ring Rotation in an Operating Engine on JSTOR

A radiotracer technique has been developed to monitor the rotational movement of piston rings during engine operation. Each ring to be monitored is modified by ...
www.jstor.org www.jstor.org

Everything You Wanted to Know about Piston Ring Grooves

Ring groove placement, size, and finish are paramount attributes to overall piston performance.
blog.wiseco.com blog.wiseco.com
"The main purpose for axial clearance is to allow the ring to spin. The cross-hatch in the cylinder walls induces rotation of the rings."
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The reason two stroke rings are pegged is to stop the end of the ring from hooking up in one of the ports
So yes the rings can turn
But I've never seen rings in any engine lined up like that
 
City Garage said:
We use total seal on all of our commando builds and actually are thinking about using them here to see if we can clean up some of the oil issues
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IMHO that is far more sensible than putting it back together with the rings orientated differently and hoping for an improvement.

With respect, you do not know that the ring gaps have caused this over oiling. It’s a correlation, it is NOT proof of causation by a long way.
 
Fast Eddie said:
IMHO that is far more sensible than putting it back together with the rings orientated differently and hoping for an improvement.

With respect, you do not know that the ring gaps have caused this over oiling. It’s a correlation, it is NOT proof of causation by a long way.
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It's a 961 so anything can happen
You'd hope that the modern oil control ring would have stopped the oil consumption to a large degree regardless of the compression rings lining up?
Total seal rings would be a great idea here
I've just used them in my b50 project it's given the bike sky high compression and zero smoke so far
 
0340, can't sleep thinking of this. I don't care if 961, Commando, or lawn mower - to the best of my knowledge and what I can find, rings that aren't pegged rotate. Anyone with an SAE account can download proof and the methodology used for testing - I don't have an account.

This article is interesting: https://www.highpowermedia.com/Arch... has,“observed to rotate as rapidly as 1 rpm”. Answered at least one of my questions.

Here's another simple "logic dictates". If rings did not rotate there would absolutely be marks in the cylinder walls showing that. At the very least at the top where only the top ring touches the cylinder wall. In the original post (if I remember right) there was mention of marks aligned with the rings - maybe something is preventing the normal rotation of the rings?
 
baz said:
The reason two stroke rings are pegged is to stop the end of the ring from hooking up in one of the ports
So yes the rings can turn
But I've never seen rings in any engine lined up like that
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I agree, however, as unpegged rings rotate then I'm sceptical of the assumption that it was due to "idiots at the factory fitting the rings incorrectly".
 
marshg246 said:
0340, can't sleep thinking of this. I don't care if 961, Commando, or lawn mower - to the best of my knowledge and what I can find, rings that aren't pegged rotate. Anyone with an SAE account can download proof and the methodology used for testing - I don't have an account.

This article is interesting: https://www.highpowermedia.com/Archive/rotation-of-piston-rings#:~:text=The speed of rotation of piston rings has,“observed to rotate as rapidly as 1 rpm”. Answered at least one of my questions.

Here's another simple "logic dictates". If rings did not rotate there would absolutely be marks in the cylinder walls showing that. At the very least at the top where only the top ring touches the cylinder wall. In the original post (if I remember right) there was mention of marks aligned with the rings - maybe something is preventing the normal rotation of the rings?
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I think the fact they are all aligned has caused the mark in the bore and that was probably stopping them rotating.

Anyway, if all three rings are in the same bore, being subjected to the same RPM, crosshatching etc. surely they would rotate in unison? So for rings that are correctly spaced @ 120° they should more or less remain that way?
 
L.A.B. said:
I agree, however, as unpegged rings rotate then I'm sceptical of the assumption that it was due to "idiots at the factory fitting the rings incorrectly".
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I'm not as skeptical :)
 
cliffa said:
Anyway, if all three rings are in the same bore, being subjected to the same RPM, crosshatching etc. surely they would rotate in unison? So for rings that are correctly spaced @ 120° they should more or less remain that way?
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Until tonight I would have agreed, and I even implied that in my first post this thread. However, the article I posted a few minutes ago disputes a lot of my thinking in that they've seen the rings rotating in different directions. Now, I'm guessing that pressures acting on the ends of the rings cause the rotation when the gasses change direction going through the gap.
 
Interesting reading. I was sure rings rotated as well and I've always spaced my ring gaps evenly with engine builds...but admittedly, I've never gone back to check...although I have one car engine I may well be doing that with..due to other issues!

Given the mileage, plus stories from ex workers saying how variable the build process was, along with a factory tour that showed even some basic quality procedures were not present, coupled with how the rings are currently lined up...I've never seen that before, I'd be pointing at the factory as well. I'd be interested in the installed ring gaps, but could easily be poor gapping, ends not chamfered after gapping coupled with poor assembly...stacking up issues.

So what's the plan of action?
 
The thing with rules about part behaviour in running engines is that they are more guidance than hard rules ;) .

Always expect the unexpected.
 
Voodooo said:
Anyone who thinks that the rings on City Garages piston rotated in that position after engine assembly are delusional.
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Strong statement from someone with absolutely no proof! Yes, it's unlikely, but then winning a 1.5+ Billon Dollar lottery is too but it has happened!
 
From the article I linked earlier:

The speed of rotation of piston rings has been measured experimentally. Shaw and Nussdorfer (2) examined the phenomenon on a large engine and found that, at 1000 rpm engine speed, the piston rings were “observed to rotate as rapidly as 1 rpm”. Jung and Jin reported in more detail: on the engine they used, at 4000 rpm and 2 bar bmep, the rings rotated at 0.6 rpm in opposite directions to each other, with the second ring initially oscillating between two positions before finally beginning to rotate continuously.

At higher load, the top ring didn’t rotate, and the second ring rotated at speeds from 0.5 to 3 rpm. On the same engine and at lower engine speed, the top ring simply moved to a given angular position and then remained stationary at 2 bar load. With an increase to 4 bar, there was a change in top ring position but still no continuous rotation. The second ring was also observed to be stationary at this speed in some tests, some of which found the ring gaps aligned – the condition where oil consumption is highest.

1. Jung, S., and Jin, J., “Monitoring of Rotational Movements of Two Piston Rings in a Cylinder Using Radioisotopes”, Journal of the Korean Nuclear Society; vol 31(4); ISSN 0372-7327, August 1999

2. Shaw, M., and Nussdorfer, T., “A Visual and Photographic Study of Cylinder Lubrication”, NACA Technical Report no 850, 1946
 
Fit the rings at 120 degrees and the bore will wear evenly all around its circumference and the rings will slowly turn until the next teardown. Fit them with the gaps in vertical row and before they get a chance an unworn vertical section will develop from the vertical ring gaps which will then stop the rings turning.
 
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marshg246 said:
Strong statement from someone with absolutely no proof! Yes, it's unlikely, but then winning a 1.5+ Billon Dollar lottery is too but it has happened!
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We have worked on a lot of 961’s and this isn’t our first rodeo with digging into the engines.

But just for the sake of argument it would be one thing if it was just one cylinder then we can say it’s lottery winning but to have both cylinders that way again lottery winning odds. both sets of rings facing rearward and vertically aligned I’m not very good at that kind of math but it seems to me the odds are staggering

We are lucky enough to work with some of the best engine builders here in California Including two people who are in our same shop complex. and while their work may not be published in the journal of Korean nuclear society as many keep keep quotibg here they have been published in many of the hot Rod and other trade magazines so I bow down to their greatness and experience when dealing with engines.

The bottom line is when we showed them what we found they Immediately said installation error without hesitation.
 
City Garage said:
The bottom line is when we showed them what we found they Immediately said installation error without hesitation.
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I would tend to agree.
QA/QC at Norton was abysmal in many respects, as we have seen from other component issues.
Norton relied a great deal on "apprentices" to do assembly operations.
Would they have known not to install the rings with the gaps aligned?
Probably not.
 
City Garage said:
We have worked on a lot of 961’s and this isn’t our first rodeo with digging into the engines.

But just for the sake of argument it would be one thing if it was just one cylinder then we can say it’s lottery winning but to have both cylinders that way again lottery winning odds. both sets of rings facing rearward and vertically aligned I’m not very good at that kind of math but it seems to me the odds are staggering

We are lucky enough to work with some of the best engine builders here in California Including two people who are in our same shop complex. and while their work may not be published in the journal of Korean nuclear society as many keep keep quotibg here they have been published in many of the hot Rod and other trade magazines so I bow down to their greatness and experience when dealing with engines.

The bottom line is when we showed them what we found they Immediately said installation error without hesitation.
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I just looked back at you original picture as I hadn't realized both pots were that way. As you say the odds on that not being an assembly error must be huge.
 
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If the rings had turned because of cross hatching or machining etc then surely every 961 would be the same? and smoking its head off the same
Is it common for 961s to smoke? And when stripped you find the rings are lined up at the front on both cylinders ?
 
baz said:
If the rings had turned because of cross hatching or machining etc then surely every 961 would be the same? and smoking its head off the same
Is it common for 961s to smoke? And when stripped you find the rings are lined up at the front on both cylinders ?
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For the first batch of 961's that can to the US in December 2013, yes they did smoke on starting - when cold.
Once they were warmed up there was no perceptible sign of smoke, but I could smell oil in the exhaust.
The mechanic who fixed mine told me that the rings where too large (wrong size) for the pistons, that the end gaps were too big, and the end gaps were in line.
The factory told my dealer that the mishap was the result of a supplier error.
If that was true, it did not bode well for the state of Norton factory QA/QC.
Incorrect parts should never find their way into inventory.
 
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