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Motorcycles » rec.motorcycles.tech » Using oversized piston rings
| Using oversized piston rings [message #507908] |
Tue, 08 November 2005 19:36 |
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Would it cause problems to take .50 oversized rings and grind the end-gap
for use on standard pistons? i.e. is the interior diameter going to be too
large, and/or would there be too much spring tension?
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| Re: Using oversized piston rings [message #507910 ] |
Tue, 08 November 2005 20:45 |
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Paul Barrett <spam [at] barrettmanor.com> wrote:
> Would it cause problems to take .50 oversized rings and grind the end-gap
> for use on standard pistons? i.e. is the interior diameter going to be too
> large, and/or would there be too much spring tension?
Um, I've actually done this, and it worked.
--
Trophy 1200 750SS XS650x2 CB400F CB125S DT50MX
GAGARPHOF#30 GHPOTHUF#1 BOTAFOT#60 ANORAK#06 YTC#3
BOF#30 WUSS#5 The bells, the bells.....
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| Re: Using oversized piston rings [message #507913 ] |
Wed, 09 November 2005 00:40 |
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"Paul Barrett" <spam [at] barrettmanor.com> wrote in message
news:Uo6dnd9xIKG9be3eRVn-sQ [at] comcast.com...
> Would it cause problems to take .50 oversized rings and grind the end-gap
> for use on standard pistons? i.e. is the interior diameter going to be
too
> large, and/or would there be too much spring tension?
>
The problem with oversized rings as opposed to oversized pistons is the
increased ring area exposed to combustion pressure. Not *necessarily* bad,
but definitely not something the engineers anticipated...
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| Re: Using oversized piston rings [message #507914 ] |
Wed, 09 November 2005 02:51 |
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The Older Gentleman wrote:
> Paul Barrett <spam [at] barrettmanor.com> wrote:
>
>
>>Would it cause problems to take .50 oversized rings and grind the end-gap
>>for use on standard pistons? i.e. is the interior diameter going to be too
>>large, and/or would there be too much spring tension?
>
>
> Um, I've actually done this, and it worked.
Were the pistons new? How big was the bore? For how long did it work?
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| Re: Using oversized piston rings [message #507915 ] |
Wed, 09 November 2005 04:18 |
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"Paul Barrett" <spam [at] barrettmanor.com> wrote in
news:Uo6dnd9xIKG9be3eRVn-sQ [at] comcast.com:
> Would it cause problems to take .50 oversized rings and grind the
> end-gap for use on standard pistons? i.e. is the interior diameter
> going to be too large, and/or would there be too much spring tension?
>
>
..050 is quite a bit. I knew a fellow that put .030 oversize in a 350 V8 and
he said it was the hardest starting SOB he ever encountered. After about
3000 miles then it started to loosen up a bit but he also added that he would
never do it again. He sold the car so the engine's longevity was never
determined.
I think that in an aluminum block, .050 oversize in a standard bore would be
a very bad thing.
pierce
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| Re: Using oversized piston rings [message #507916 ] |
Wed, 09 November 2005 04:51 |
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Paul Barrett wrote:
> Would it cause problems to take .50 oversized rings and grind the end-gap
> for use on standard pistons? i.e. is the interior diameter going to be too
> large, and/or would there be too much spring tension?
1. Do you have any relatives named "Nomen Nescio" by any chance?
2. What kind of motorbike or engine are you talking about anyway>
3. Are you talking about 1/2 an inch or half a millimeter oversize?
4. Is the engine a 2-stroke or a 4-stroke? An oversize ring might tend
to snag in 2-stroke ports worse than the right sized ring.
5. How large is the bore of the piston? Large bore pistons around 100mm
in diameter probably would probably tolerate the oversized ring better
than smaller bore pistons around 50mm.
6. Radial spring tension isn't the major compression sealing force on a
ring. It's the hot combustion gasses between the piston and the ring
that push the ring against the cylinder wall. Will there be enough
space behind the ring to allow the passage of gasses?
7. You could carefully measure the cylinder bore with an internal
micrometer, somehow measure the diameter of the ring groove (a vernier
caliper jaw won't fit in there), and calculate whether there would be
adequate space left behind the ring.
8. Is there some particular reason why you want to risk destroying an
engine in order to use an oversized ring with a standard piston?
9. Has Abby ever had any purebred Abbysinian kittens? I want one!
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| Re: Using oversized piston rings [message #507917 ] |
Wed, 09 November 2005 05:15 |
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This is in a 1980 CB750, so it's a 4-stroke with 62mm dia. pistons. The
rings in question were .50mm (2 sizes) over, which I ground to the proper
end-gap for my standard-bore cylinders & pistons. I had seen postings of
this being done one size over to get a better than out-of-the-box end-gap.
I just didn't know if going 2 sizes over was going too far. I had no *good*
reason - just I had the rings on-hand and got in a hurry.
Sorry, kittens are not in the cards I'm afraid.
"skimmer" <rynchops_niger [at] yahoo.com> wrote in message
news:1131508311.382298.83220 [at] g47g2000cwa.googlegroups.com...
>
> Paul Barrett wrote:
>> Would it cause problems to take .50 oversized rings and grind the end-gap
>> for use on standard pistons? i.e. is the interior diameter going to be
>> too
>> large, and/or would there be too much spring tension?
>
> 1. Do you have any relatives named "Nomen Nescio" by any chance?
>
> 2. What kind of motorbike or engine are you talking about anyway>
>
> 3. Are you talking about 1/2 an inch or half a millimeter oversize?
>
> 4. Is the engine a 2-stroke or a 4-stroke? An oversize ring might tend
> to snag in 2-stroke ports worse than the right sized ring.
>
> 5. How large is the bore of the piston? Large bore pistons around 100mm
> in diameter probably would probably tolerate the oversized ring better
> than smaller bore pistons around 50mm.
>
> 6. Radial spring tension isn't the major compression sealing force on a
> ring. It's the hot combustion gasses between the piston and the ring
> that push the ring against the cylinder wall. Will there be enough
> space behind the ring to allow the passage of gasses?
>
> 7. You could carefully measure the cylinder bore with an internal
> micrometer, somehow measure the diameter of the ring groove (a vernier
> caliper jaw won't fit in there), and calculate whether there would be
> adequate space left behind the ring.
>
> 8. Is there some particular reason why you want to risk destroying an
> engine in order to use an oversized ring with a standard piston?
>
> 9. Has Abby ever had any purebred Abbysinian kittens? I want one!
>
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| Re: Using oversized piston rings [message #507920 ] |
Wed, 09 November 2005 08:15 |
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Matt <themattfella [at] xxyyyzzzz.com> wrote:
> > Um, I've actually done this, and it worked.
>
> Were the pistons new? How big was the bore? For how long did it work?
Standard pistons, standard bores, and it worked fine - the bike got
nicked a few months later, mind. It was a Honda CB175cc twin.
But it didn't use oil or smoke.
A complete bodge, I agree. I was a teenager then. But it worked.
--
Trophy 1200 750SS XS650x2 CB400F CB125S DT50MX
GAGARPHOF#30 GHPOTHUF#1 BOTAFOT#60 ANORAK#06 YTC#3
BOF#30 WUSS#5 The bells, the bells.....
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| Re: Using oversized piston rings [message #507921 ] |
Wed, 09 November 2005 08:29 |
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Paul Barrett wrote:
> This is in a 1980 CB750, so it's a 4-stroke with 62mm dia. pistons. The
> rings in question were .50mm (2 sizes) over, which I ground to the proper
> end-gap for my standard-bore cylinders & pistons. I had seen postings of
> this being done one size over to get a better than out-of-the-box end-gap.
> I just didn't know if going 2 sizes over was going too far. I had no *good*
> reason - just I had the rings on-hand and got in a hurry.
So half a millimeter is 0.0197 and half of that is 0.00985 inches that
the inside of the rings will have to move toward the piston on each
side.
I wonder if plastigauge is made that thick?
It seems that if you could lay a strip of plastic behind a ring, insert
it into the cylinder past the chamfer using two screwdrivers so you
could get the piston in without overly-compressing the ring, and then
removing the plastigauge, you could see if the plastigauge crushed when
the ring was evenly compressed all the way around.
But that's still a *cold* test. How much is the ring going to expand
when it gets hit by 900-degree F combustion gasses at about 900 pounds
of pressure?
Mechanics are given an end gap number so they will know if the ring is
going to have enough room to grow with heat.
What does Plano, TX look like these days? Plano, CA looks like a soggy
cow pasture as I look out across the settling basins. There are Canada
Geese out there every morning among the cattle.
It seems like some cowardly Texans vamoosed out of Plano, TX in 1861,
and headed for the California gold fields instead of joining up with
the Confederacy. But they got here and looked around and saw how nice
the soil was by the river, so they stayed and called it Plano.
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| Re: Using oversized piston rings [message #507922 ] |
Wed, 09 November 2005 08:29 |
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Paul Barrett wrote:
> This is in a 1980 CB750, so it's a 4-stroke with 62mm dia. pistons. The
> rings in question were .50mm (2 sizes) over, which I ground to the proper
> end-gap for my standard-bore cylinders & pistons. I had seen postings of
> this being done one size over to get a better than out-of-the-box end-gap.
> I just didn't know if going 2 sizes over was going too far. I had no *good*
> reason - just I had the rings on-hand and got in a hurry.
>
> Sorry, kittens are not in the cards I'm afraid.
>
>
> "skimmer" <rynchops_niger [at] yahoo.com> wrote in message
> news:1131508311.382298.83220 [at] g47g2000cwa.googlegroups.com...
>
>>Paul Barrett wrote:
>>
>>>Would it cause problems to take .50 oversized rings and grind the end-gap
>>>for use on standard pistons? i.e. is the interior diameter going to be
>>>too
>>>large, and/or would there be too much spring tension?
>>
>>1. Do you have any relatives named "Nomen Nescio" by any chance?
>>
>>2. What kind of motorbike or engine are you talking about anyway>
>>
>>3. Are you talking about 1/2 an inch or half a millimeter oversize?
>>
>>4. Is the engine a 2-stroke or a 4-stroke? An oversize ring might tend
>>to snag in 2-stroke ports worse than the right sized ring.
>>
>>5. How large is the bore of the piston? Large bore pistons around 100mm
>>in diameter probably would probably tolerate the oversized ring better
>>than smaller bore pistons around 50mm.
>>
>>6. Radial spring tension isn't the major compression sealing force on a
>>ring. It's the hot combustion gasses between the piston and the ring
>>that push the ring against the cylinder wall. Will there be enough
>>space behind the ring to allow the passage of gasses?
>>
>>7. You could carefully measure the cylinder bore with an internal
>>micrometer, somehow measure the diameter of the ring groove (a vernier
>>caliper jaw won't fit in there), and calculate whether there would be
>>adequate space left behind the ring.
>>
>>8. Is there some particular reason why you want to risk destroying an
>>engine in order to use an oversized ring with a standard piston?
>>
>>9. Has Abby ever had any purebred Abbysinian kittens? I want one!
>>
>
>
>
New rings on a old piston is always less than an ideal situation, as the
rings will never seat fully in the ringlands..
J.
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| Re: Using oversized piston rings [message #507923 ] |
Wed, 09 November 2005 08:40 |
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P.J. Berg <BergRace [at] gmail.com> wrote:
> New rings on a old piston is always less than an ideal situation, as the
> rings will never seat fully in the ringlands
That statement is interesting, because it goes against accepted practice
on high performance two-strokes for the last 30+ years.
In other words, for two-strokes at least, it's cobblers.
--
Trophy 1200 750SS XS650x2 CB400F CB125S DT50MX
GAGARPHOF#30 GHPOTHUF#1 BOTAFOT#60 ANORAK#06 YTC#3
BOF#30 WUSS#5 The bells, the bells.....
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| Re: Using oversized piston rings [message #507925 ] |
Wed, 09 November 2005 11:04 |
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"P.J. Berg" <BergRace [at] gmail.com> wrote in
news:Gzhcf.596$zc1.582 [at] amstwist00:
> New rings on a old piston is always less than an ideal situation, as the
> rings will never seat fully in the ringlands..
>
> J.
Since when?
pierce
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| Re: Using oversized piston rings [message #507927 ] |
Wed, 09 November 2005 17:58 |
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Paul Barrett wrote:
> Would it cause problems to take .50 oversized rings and grind the end-gap
> for use on standard pistons? i.e. is the interior diameter going to be too
> large, and/or would there be too much spring tension?
>
>
I've done it with a 2smoke. Worked out well and hasn't spit out the
rings yet.
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| Re: Using oversized piston rings [message #507928 ] |
Wed, 09 November 2005 18:39 |
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The Older Gentleman wrote:
> P.J. Berg <BergRace [at] gmail.com> wrote:
>
>
>>New rings on a old piston is always less than an ideal situation, as the
>>rings will never seat fully in the ringlands
>
>
>
> That statement is interesting, because it goes against accepted practice
> on high performance two-strokes for the last 30+ years.
>
> In other words, for two-strokes at least, it's cobblers.
>
>
Nope, in high performance Two-stroke we used to hone the cylinder for
the next ring/piston size. These days you do not hone, merely measure
the wear and fit a proper sized piston with rings..
(Aircooled 100cc go-kart engines at aprox 18000 rpm.)
J.
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| Re: Using oversized piston rings [message #507929 ] |
Wed, 09 November 2005 18:40 |
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R. Pierce Butler wrote:
> "P.J. Berg" <BergRace [at] gmail.com> wrote in
> news:Gzhcf.596$zc1.582 [at] amstwist00:
>
>
>
>>New rings on a old piston is always less than an ideal situation, as the
>>rings will never seat fully in the ringlands..
>>
>>J.
>
>
> Since when?
>
> pierce
>
Since dawn of the internal combustion engine...
J.
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| Re: Using oversized piston rings [message #507930 ] |
Wed, 09 November 2005 19:55 |
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P.J. Berg <BergRace [at] gmail.com> wrote:
> The Older Gentleman wrote:
> > P.J. Berg <BergRace [at] gmail.com> wrote:
> >
> >
> >>New rings on a old piston is always less than an ideal situation, as the
> >>rings will never seat fully in the ringlands
> >
> >
> >
> > That statement is interesting, because it goes against accepted practice
> > on high performance two-strokes for the last 30+ years.
> >
> > In other words, for two-strokes at least, it's cobblers.
> >
> >
> Nope, in high performance Two-stroke we used to hone the cylinder for
> the next ring/piston size. These days you do not hone, merely measure
> the wear and fit a proper sized piston with rings..
>
> (Aircooled 100cc go-kart engines at aprox 18000 rpm.)
>
I can see you might for an 18,000rpm race engine, but for road engines,
you simply re-ring. This is in some manufacturers' service advice, too.
--
Trophy 1200 750SS XS650x2 CB400F CB125S DT50MX
GAGARPHOF#30 GHPOTHUF#1 BOTAFOT#60 ANORAK#06 YTC#3
BOF#30 WUSS#5 The bells, the bells.....
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| Re: Using oversized piston rings [message #507931 ] |
Wed, 09 November 2005 20:45 |
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Rick Cortese wrote:
> Paul Barrett wrote:
>
>> Would it cause problems to take .50 oversized rings and grind the
>> end-gap for use on standard pistons? i.e. is the interior diameter
>> going to be too large, and/or would there be too much spring tension?
>>
>>
>
> I've done it with a 2smoke. Worked out well and hasn't spit out the
> rings yet.
It will always work, my statement was that the solution is less than
ideal, as you will get more blowby compared to fitting a new piston with
new rings.
J.
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| Re: Using oversized piston rings [message #507932 ] |
Wed, 09 November 2005 20:48 |
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The Older Gentleman wrote:
> P.J. Berg <BergRace [at] gmail.com> wrote:
>
>
>>The Older Gentleman wrote:
>>
>>>P.J. Berg <BergRace [at] gmail.com> wrote:
>>>
>>>
>>>
>>>>New rings on a old piston is always less than an ideal situation, as the
>>>>rings will never seat fully in the ringlands
>>>
>>>
>>>
>>>That statement is interesting, because it goes against accepted practice
>>>on high performance two-strokes for the last 30+ years.
>>>
>>>In other words, for two-strokes at least, it's cobblers.
>>>
>>>
>>
>>Nope, in high performance Two-stroke we used to hone the cylinder for
>>the next ring/piston size. These days you do not hone, merely measure
>>the wear and fit a proper sized piston with rings..
>>
>>(Aircooled 100cc go-kart engines at aprox 18000 rpm.)
>>
>
> I can see you might for an 18,000rpm race engine, but for road engines,
> you simply re-ring. This is in some manufacturers' service advice, too.
>
>
My statement was:
"New rings on a old piston is always less than an ideal situation"
With emphasis on "less than ideal" as in increased blowby compared to
using a new piston with new rings.
J.
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| Re: Using oversized piston rings [message #507933 ] |
Wed, 09 November 2005 23:16 |
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P.J. Berg <BergRace [at] gmail.com> wrote:
> The Older Gentleman wrote:
> > P.J. Berg <BergRace [at] gmail.com> wrote:
> >
> >
> >>The Older Gentleman wrote:
> >>
> >>>P.J. Berg <BergRace [at] gmail.com> wrote:
> >>>
> >>>
> >>>
> >>>>New rings on a old piston is always less than an ideal situation, as the
> >>>>rings will never seat fully in the ringlands
> >>>
> >>>
> >>>
> >>>That statement is interesting, because it goes against accepted practice
> >>>on high performance two-strokes for the last 30+ years.
> >>>
> >>>In other words, for two-strokes at least, it's cobblers.
> >>>
> >>>
> >>
> >>Nope, in high performance Two-stroke we used to hone the cylinder for
> >>the next ring/piston size. These days you do not hone, merely measure
> >>the wear and fit a proper sized piston with rings..
> >>
> >>(Aircooled 100cc go-kart engines at aprox 18000 rpm.)
> >>
> >
> > I can see you might for an 18,000rpm race engine, but for road engines,
> > you simply re-ring. This is in some manufacturers' service advice, too.
> >
> >
>
> My statement was:
> "New rings on a old piston is always less than an ideal situation"
> With emphasis on "less than ideal" as in increased blowby compared to
> using a new piston with new rings.
>
Hair-splitting. In practice, it makes sod-all difference.
--
Trophy 1200 750SS XS650x2 CB400F CB125S DT50MX
GAGARPHOF#30 GHPOTHUF#1 BOTAFOT#60 ANORAK#06 YTC#3
BOF#30 WUSS#5 The bells, the bells.....
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| Re: Using oversized piston rings [message #507934 ] |
Wed, 09 November 2005 23:16 |
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P.J. Berg <BergRace [at] gmail.com> wrote:
> Rick Cortese wrote:
> > Paul Barrett wrote:
> >
> >> Would it cause problems to take .50 oversized rings and grind the
> >> end-gap for use on standard pistons? i.e. is the interior diameter
> >> going to be too large, and/or would there be too much spring tension?
> >>
> >>
> >
> > I've done it with a 2smoke. Worked out well and hasn't spit out the
> > rings yet.
>
> It will always work, my statement was that the solution is less than
> ideal, as you will get more blowby compared to fitting a new piston with
> new rings.
>
Do I detect some frantic justification and dissembling?
--
Trophy 1200 750SS XS650x2 CB400F CB125S DT50MX
GAGARPHOF#30 GHPOTHUF#1 BOTAFOT#60 ANORAK#06 YTC#3
BOF#30 WUSS#5 The bells, the bells.....
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| Re: Using oversized piston rings [message #507936 ] |
Thu, 10 November 2005 00:34 |
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P.J. Berg wrote:
> Rick Cortese wrote:
>
>> Paul Barrett wrote:
>>
>>> Would it cause problems to take .50 oversized rings and grind the
>>> end-gap for use on standard pistons? i.e. is the interior diameter
>>> going to be too large, and/or would there be too much spring tension?
>>>
>>>
>>
>> I've done it with a 2smoke. Worked out well and hasn't spit out the
>> rings yet.
>
>
> It will always work, my statement was that the solution is less than
> ideal, as you will get more blowby compared to fitting a new piston with
> new rings.
Actually that isn't exactly what I did. Vintage bike and I found a NOS
piston the right size but the only rings I could find in ~6 months of
looking were oversized. I just ground down the ends until the rings had
the right end gap in the cylinder.
There was a lot of spring tension against the cylinder because of the
larger radius rings and with the new piston it sealed up nice.
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| Re: Using oversized piston rings [message #507942 ] |
Thu, 10 November 2005 16:28 |
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i would if they're straight-end rings.
i usually figure about .003" of gap per inch of diameter on water cooled
engines.
good luck, sammm
"Paul Barrett" <spam [at] barrettmanor.com> wrote in message
news:Uo6dnd9xIKG9be3eRVn-sQ [at] comcast.com...
> Would it cause problems to take .50 oversized rings and grind the end-gap
> for use on standard pistons? i.e. is the interior diameter going to be
> too large, and/or would there be too much spring tension?
>
>
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| Re: Using oversized piston rings [message #507943 ] |
Thu, 10 November 2005 17:53 |
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The Older Gentleman wrote:
> P.J. Berg <BergRace [at] gmail.com> wrote:
>
>
>>Rick Cortese wrote:
>>
>>>Paul Barrett wrote:
>>>
>>>
>>>>Would it cause problems to take .50 oversized rings and grind the
>>>>end-gap for use on standard pistons? i.e. is the interior diameter
>>>>going to be too large, and/or would there be too much spring tension?
>>>>
>>>>
>>>
>>>I've done it with a 2smoke. Worked out well and hasn't spit out the
>>>rings yet.
>>
>>It will always work, my statement was that the solution is less than
>>ideal, as you will get more blowby compared to fitting a new piston with
>>new rings.
>>
>
> Do I detect some frantic justification and dissembling?
>
>
>
Far from it, two questions from two people, two answers...
J.
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| Re: Using oversized piston rings [message #507944 ] |
Thu, 10 November 2005 19:43 |
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Paul Barrett wrote:
> Would it cause problems to take .50 oversized rings and grind the end-gap
> for use on standard pistons? i.e. is the interior diameter going to be too
> large, and/or would there be too much spring tension?
Obviously it would be suboptimal according to manufacturers' standards.
I don't see that anybody has offered standard knowledge or experience
with the long-term effects, so I offer the partial results of a thought
experiment.
The rings would bear unevenly on the insides of the cylinders, and with
a greater-than-standard total force. There would be a couple of high
points on the circumference of each ring. I would expect those high
points to fall into troughs that would eventually be worn into the
cylinder walls as the rings stop rotating in the piston grooves. Each
cylinder would develop an oblong cross section. I would expect problems
with ring and cylinder lubrication after the rings stop rotating.
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| Re: Using oversized piston rings [message #507946 ] |
Thu, 10 November 2005 20:18 |
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Matt wrote:
> Obviously it would be suboptimal according to manufacturers' standards.
> I don't see that anybody has offered standard knowledge or experience
> with the long-term effects, so I offer the partial results of a thought
> experiment.
Be careful about how much you play with your brain. I've heard you'll
go blind ;-)
>
> The rings would bear unevenly on the insides of the cylinders, and with
> a greater-than-standard total force. There would be a couple of high
> points on the circumference of each ring. I would expect those high
> points to fall into troughs that would eventually be worn into the
> cylinder walls as the rings stop rotating in the piston grooves. Each
> cylinder would develop an oblong cross section. I would expect problems
> with ring and cylinder lubrication after the rings stop rotating.
And some rings don't rotate at all. Two-stroke rings have pins to
prevent the ends from rotating out into the exhaust port and snagging.
Apparently all of this commotion about fitting oversized rings---which
I'd never heard of before---is to optimize the ring gap to reduce
compression leaks to the smallest possible amount.
But ring manufacturers advise engine rebuilders to stagger the end gaps
120 degrees apart on a 3-ring piston to provide a tortuous path for
what minuscule amount of hot gas does slip through the tiny end gap.
With three gaps, the gasses will have to go 2/3rds of the way around
the piston to get to the crankcase...
And then consider the time aspect when an engine is operating at, say,
12K RPM.
It completes 200 revolutions in a single second. A complete revolution
takes place in 0.005 seconds. But the amount of time that a piston ring
is "seeing" a large pressure, starting at around 900 PSI and declining
to maybe 20 psi is about 90 to 120 degrees of revolution. And even this
event occurs only once every *fourth* stroke.
I think we are talking about how much hot gas can leak past a ring gap
in a bit over a thousandth of a second, folks. I wonder how much of
this precious combustion gas we can afford to lose?
Are we gonna run out of combustion gasses and have to go to electric
motors because of the horrendous losses? Will we have to go to fuel
cells or a hydrogen technology just because of end gap blowby?
It staggers the imagination! And now my vision's getting blurry! I
think I'm going blind, Matt!
Maybe this whole concept is like penis enlargement. Obviously,
everybody in the world (except me) needs a bigger penis.
The performance enthusiast's penis has wheels attached. This dedicated
amateur performance tuner decides that he needs a better diagnostic
tool than a compression tester, so he runs out and buys a *leak down
tester* and he pressures his cylinder and watches to see how much
static leak down he's getting.
Once he sees that he's losing his "purity of essence" through the ring
end gaps, he tears the engine down and installs over-sized rings so he
can reduce his end gap and save the essential combustion gasses.
I'll bet the static leak down fan is thrilled to death by how "tight"
his engine is!
But you don't make any power when the piston isn't moving, so the
tightest engine in the world is about as useless as a nun on Thursday.
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| Re: Using oversized piston rings [message #507947 ] |
Thu, 10 November 2005 20:37 |
|
skimmer <rynchops_niger [at] yahoo.com> wrote:
> Apparently all of this commotion about fitting oversized rings---which
> I'd never heard of before---is to optimize the ring gap to reduce
> compression leaks to the smallest possible amount.
I did it because I got sold the wrong size ring and couldn't be arsed to
go back, get them changed, etc etc.
And I was a teenager, like I said.
Anyway, it worked for me and worked for the other poster here who's done
it, so end of story, really.
--
Trophy 1200 750SS XS650x2 CB400F CB125S DT50MX
GAGARPHOF#30 GHPOTHUF#1 BOTAFOT#60 ANORAK#06 YTC#3
BOF#30 WUSS#5 The bells, the bells.....
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| Re: Using oversized piston rings [message #507952 ] |
Fri, 11 November 2005 02:26 |
|
"R. Pierce Butler" <spamsucks [at] google.com> wrote in message
news:Xns9708D8CA5B7E2mc2500183316chgoill [at] 10.232.1.1...
> "Paul Barrett" <spam [at] barrettmanor.com> wrote in
> news:Uo6dnd9xIKG9be3eRVn-sQ [at] comcast.com:
>
>> Would it cause problems to take .50 oversized rings and grind the
>> end-gap for use on standard pistons? i.e. is the interior diameter
>> going to be too large, and/or would there be too much spring tension?
>>
>>
>
> .050 is quite a bit. I knew a fellow that put .030 oversize in a 350 V8
> and
> he said it was the hardest starting SOB he ever encountered. After about
> 3000 miles then it started to loosen up a bit but he also added that he
> would
> never do it again. He sold the car so the engine's longevity was never
> determined.
>
That's horse shit! You can't stuff 0.030" oversize pistons in a standard
bore! They just won't fit!
And the OP is talking about millimeters not inches. 0.50 mm over size rings
are only 0.0196" oversize.
Diablo
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| Re: Using oversized piston rings [message #507953 ] |
Fri, 11 November 2005 04:40 |
|
"diablo" <nomail [at] spam.not> wrote in message
news:Bu6dnSt4N9_dbu7enZ2dnUVZ_vidnZ2d [at] giganews.com...
>
> "R. Pierce Butler" <spamsucks [at] google.com> wrote in message
> news:Xns9708D8CA5B7E2mc2500183316chgoill [at] 10.232.1.1...
>> "Paul Barrett" <spam [at] barrettmanor.com> wrote in
>> news:Uo6dnd9xIKG9be3eRVn-sQ [at] comcast.com:
>>
>>> Would it cause problems to take .50 oversized rings and grind the
>>> end-gap for use on standard pistons? i.e. is the interior diameter
>>> going to be too large, and/or would there be too much spring tension?
>>>
>>>
>>
>> .050 is quite a bit. I knew a fellow that put .030 oversize in a 350 V8
>> and
>> he said it was the hardest starting SOB he ever encountered. After about
>> 3000 miles then it started to loosen up a bit but he also added that he
>> would
>> never do it again. He sold the car so the engine's longevity was never
>> determined.
>>
>
>
> That's horse shit! You can't stuff 0.030" oversize pistons in a standard
> bore! They just won't fit!
>
> And the OP is talking about millimeters not inches. 0.50 mm over size
> rings are only 0.0196" oversize.
The OP was talking about oversized rings on standard pistons, same as "R.
Pierce Butler". This could be done by filing the ends to get the correct
gap. I wouldn't do it, but I won't say it wouldn't work either.
Les
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| Re: Using oversized piston rings [message #517122 ] |
Fri, 11 November 2005 21:53 |
|
"les" <oktr6r [at] cox.chrome.net> wrote in
news:ipUcf.270$QW2.190 [at] dukeread08:
> "diablo" wrote ...
>> "R. Pierce Butler" wrote ...
>>> "Paul Barrett" wrote:
>>>
>>>> Would it cause problems to take .50 oversized rings and grind the
>>>> end-gap for use on standard pistons? i.e. is the interior diameter
>>>> going to be too large, and/or would there be too much spring
>>>> tension?
>>>
>>> .050 is quite a bit. I knew a fellow that put .030 oversize in a
>>> 350 V8 and he said it was the hardest starting SOB he ever
>>> encountered. After about 3000 miles then it started to loosen up a
>>> bit but he also added that he would never do it again. He sold the
>>> car so the engine's longevity was never determined.
>>
>> That's horse shit! You can't stuff 0.030" oversize pistons in a
>> standard bore! They just won't fit!
>>
>> And the OP is talking about millimeters not inches. 0.50 mm over size
>> rings are only 0.0196" oversize.
>
> The OP was talking about oversized rings on standard pistons, same as
> "R. Pierce Butler". This could be done by filing the ends to get the
> correct gap. I wouldn't do it, but I won't say it wouldn't work
> either.
0.0196 rounds off to 0.020 in. Difference between a 0.5 mm over and
0.03 inch over is only 0.01 inch so it's not that much. Difference in
radius for 0.03 in. over is only 0.094 in. For say a 4 inch dia.
piston, that is only 2% change, so I doubt spring tension was an issue.
I somehow feel something else was going on. Did V-8 installer ensure he
had correct ring gap after filing and correct ring fit in groove, same
ring width as original?
--
HPT
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| Re: Using oversized piston rings [message #517151 ] |
Sun, 13 November 2005 07:30 |
|
Paul Barrett wrote:
> This is in a 1980 CB750, so it's a 4-stroke with 62mm dia. pistons. The
> rings in question were .50mm (2 sizes) over, which I ground to the proper
> end-gap for my standard-bore cylinders & pistons. I had seen postings of
> this being done one size over to get a better than out-of-the-box end-gap.
> I just didn't know if going 2 sizes over was going too far. I had no *good*
> reason - just I had the rings on-hand and got in a hurry.
>
> Sorry, kittens are not in the cards I'm afraid.
>
>
> "skimmer" <rynchops_niger [at] yahoo.com> wrote in message
> news:1131508311.382298.83220 [at] g47g2000cwa.googlegroups.com...
>> Paul Barrett wrote:
>>> Would it cause problems to take .50 oversized rings and grind the end-gap
>>> for use on standard pistons? i.e. is the interior diameter going to be
>>> too
>>> large, and/or would there be too much spring tension?
>> 1. Do you have any relatives named "Nomen Nescio" by any chance?
>>
>> 2. What kind of motorbike or engine are you talking about anyway>
>>
>> 3. Are you talking about 1/2 an inch or half a millimeter oversize?
>>
>> 4. Is the engine a 2-stroke or a 4-stroke? An oversize ring might tend
>> to snag in 2-stroke ports worse than the right sized ring.
>>
>> 5. How large is the bore of the piston? Large bore pistons around 100mm
>> in diameter probably would probably tolerate the oversized ring better
>> than smaller bore pistons around 50mm.
>>
>> 6. Radial spring tension isn't the major compression sealing force on a
>> ring. It's the hot combustion gasses between the piston and the ring
>> that push the ring against the cylinder wall. Will there be enough
>> space behind the ring to allow the passage of gasses?
>>
>> 7. You could carefully measure the cylinder bore with an internal
>> micrometer, somehow measure the diameter of the ring groove (a vernier
>> caliper jaw won't fit in there), and calculate whether there would be
>> adequate space left behind the ring.
>>
>> 8. Is there some particular reason why you want to risk destroying an
>> engine in order to use an oversized ring with a standard piston?
>>
>> 9. Has Abby ever had any purebred Abbysinian kittens? I want one!
>>
>
>
Just from an engineering point of view, a .5 mm (about .020) oversize
piston ring is ground "round" at that diameter.
If it is used in a smaller bore (on a smaller piston), it is no longer
circular even though you've ground down the ends to have the correct end
gap.
I know it's not much out of circularity, but the "hoop stress" that a
piston ring imparts is a function of how circular, and consequently, how
even is that stress distributed.
But, if someone has done it and it has worked... hey, what do I know?
CP
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| Re: Using oversized piston rings [message #517191 ] |
Mon, 14 November 2005 19:01 |
|
Peter V wrote:
> But, if someone has done it and it has worked... hey, what do I know?
Nobody on this thread has offered experience regarding the long-term
effects of using oversize rings.
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| Re: Using oversized piston rings [message #517192 ] |
Mon, 14 November 2005 19:54 |
|
Matt wrote:
> Peter V wrote:
>
> > But, if someone has done it and it has worked... hey, what do I know?
>
> Nobody on this thread has offered experience regarding the long-term
> effects of using oversize rings.
Somebody who would use oversized rings to reduce the leakage past the
end gaps probably wouldn't care about the long-term effects, they'd be
chasing the immediate mouse milk.
You have to milk a lot of mice to get a drop of milk...
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| Re: Using oversized piston rings [message #517194 ] |
Mon, 14 November 2005 20:10 |
|
Matt <themattfella [at] xxyyyzzzz.com> wrote:
> Peter V wrote:
>
> > But, if someone has done it and it has worked... hey, what do I know?
>
> Nobody on this thread has offered experience regarding the long-term
> effects of using oversize rings.
Who cares?
--
Trophy 1200 750SS XS650x2 CB400F CB125S DT50MX
GAGARPHOF#30 GHPOTHUF#1 BOTAFOT#60 ANORAK#06 YTC#3
BOF#30 WUSS#5 The bells, the bells.....
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| Re: Using oversized piston rings [message #517197 ] |
Tue, 15 November 2005 01:33 |
|
Matt <themattfella [at] xxyyyzzzz.com> wrote in news:Ah4ef.13092$cg.6711
[at] news02.roc.ny:
> Peter V wrote:
>
>> But, if someone has done it and it has worked... hey, what do I know?
>
> Nobody on this thread has offered experience regarding the long-term
> effects of using oversize rings.
That is quite true. Most people do things by the book.
My father had a strange air cooled engine that he needed rings for. There
were no piston rings available at the time so he grabbed a book of the
various automotive piston rings available and found that he could use piston
rings from a Packard. They fit so he used them.
pierce
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| Re: Using oversized piston rings [message #517199 ] |
Tue, 15 November 2005 02:17 |
|
The Older Gentleman wrote:
> Matt <themattfella [at] xxyyyzzzz.com> wrote:
>
>
>>Peter V wrote:
>>
>>
>>>But, if someone has done it and it has worked... hey, what do I know?
>>
>>Nobody on this thread has offered experience regarding the long-term
>>effects of using oversize rings.
>
>
> Who cares?
>
>
probably not anybody who expects to be kicking the bucket soon
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| Re: Using oversized piston rings [message #517202 ] |
Tue, 15 November 2005 08:17 |
|
Matt <themattfella [at] xxyyyzzzz.com> wrote:
> The Older Gentleman wrote:
> > Matt <themattfella [at] xxyyyzzzz.com> wrote:
> >
> >
> >>Peter V wrote:
> >>
> >>
> >>>But, if someone has done it and it has worked... hey, what do I know?
> >>
> >>Nobody on this thread has offered experience regarding the long-term
> >>effects of using oversize rings.
> >
> >
> > Who cares?
> >
> >
>
> probably not anybody who expects to be kicking the bucket soon
You're not very bright, really, are you?
--
Trophy 1200 750SS XS650x2 CB400F CB125S DT50MX
GAGARPHOF#30 GHPOTHUF#1 BOTAFOT#60 ANORAK#06 YTC#3
BOF#30 WUSS#5 The bells, the bells.....
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| Re: Using oversized piston rings [message #517203 ] |
Tue, 15 November 2005 10:41 |
|
The Older Gentleman wrote:
> Matt <themattfella [at] xxyyyzzzz.com> wrote:
>
>
>>Peter V wrote:
>>
>>
>>>But, if someone has done it and it has worked... hey, what do I know?
>>
>>Nobody on this thread has offered experience regarding the long-term
>>effects of using oversize rings.
>
>
> Who cares?
Hey, did you get an insurance payment for that messed-up CB175 that got
stolen?
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| Re: Using oversized piston rings [message #517205 ] |
Tue, 15 November 2005 20:02 |
|
Matt <themattfella [at] xxyyyzzzz.com> wrote:
> The Older Gentleman wrote:
> > Matt <themattfella [at] xxyyyzzzz.com> wrote:
> >
> >
> >>Peter V wrote:
> >>
> >>
> >>>But, if someone has done it and it has worked... hey, what do I know?
> >>
> >>Nobody on this thread has offered experience regarding the long-term
> >>effects of using oversize rings.
> >
> >
> > Who cares?
>
> Hey, did you get an insurance payment for that messed-up CB175 that got
> stolen?
What messed-up CB175?
If you mean my bloody nice, clean, sparkling and sweet-running bike,
then yes. More than I'd paid for it, too :-))
--
Trophy 1200 750SS XS650x2 CB400F CB125S DT50MX
GAGARPHOF#30 GHPOTHUF#1 BOTAFOT#60 ANORAK#06 YTC#3
BOF#30 WUSS#5 The bells, the bells.....
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| Re: Using oversized piston rings [message #517208 ] |
Tue, 15 November 2005 20:20 |
|
The Older Gentleman wrote:
> Matt <themattfella [at] xxyyyzzzz.com> wrote:
>
>
>>The Older Gentleman wrote:
>>
>>>Matt <themattfella [at] xxyyyzzzz.com> wrote:
>>>
>>>
>>>
>>>>Peter V wrote:
>>>>
>>>>
>>>>
>>>>>But, if someone has done it and it has worked... hey, what do I know?
>>>>
>>>>Nobody on this thread has offered experience regarding the long-term
>>>>effects of using oversize rings.
>>>
>>>
>>>Who cares?
>>
>>Hey, did you get an insurance payment for that messed-up CB175 that got
>>stolen?
>
>
> What messed-up CB175?
>
> If you mean my bloody nice, clean, sparkling and sweet-running bike,
> then yes. More than I'd paid for it, too :-))
I mean the one that had wrong-size piston rings.
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| Re: Using oversized piston rings [message #517210 ] |
Tue, 15 November 2005 20:50 |
|
Matt <themattfella [at] xxyyyzzzz.com> wrote:
<snip>
<loses patience>
Do fuck off, you pathetic, inadequate, unprincipled, nasty, stupid,
vindictive, childish little by-product of an inbred village idiot's
wank.
--
Trophy 1200 750SS XS650x2 CB400F CB125S DT50MX
GAGARPHOF#30 GHPOTHUF#1 BOTAFOT#60 ANORAK#06 YTC#3
BOF#30 WUSS#5 The bells, the bells.....
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