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This year's annual



 
 
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  #21  
Old November 5th 06, 07:13 PM posted to rec.aviation.owning
RST Engineering
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Default This year's annual

Now I would never, ever do this myself. Nor would I ever think of doing it
to an airplane. However, I have this friend named Ernie that told me about
it.

You have a low compression cylinder that you believe to be stuck rings. You
pull the top plug and put the cylinder on the compression stroke at TDC.
You pour Marvel Oil into the cylinder until it is full right up to the plug
threads. You leave it 24 hours, rocking the prop back and forth a few
degrees every so often. Drain the MMO out the bottom plug, replace both
plugs and go fly half an hour.

According to Ernie, 99% cure rate.

Jim



"B A R R Y" wrote in message
...
On 5 Nov 2006 06:09:49 -0800, "Jay Honeck" wrote:


Was this due to lead fouling?


It was due to something fouling, maybe lead, maybe coke...



  #22  
Old November 5th 06, 11:33 PM posted to rec.aviation.owning
A Lieberma
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Posts: 318
Default This year's annual

B A R R Y wrote in
:

In my case, the fouling was on valve seats.

How would a fouled plug kill compression? G


Duh good point. Not exactly sparking is it during the test?

Told ya I wasn't mechanically inclined!!!

Allen
  #23  
Old November 6th 06, 04:44 PM posted to rec.aviation.owning
[email protected]
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Default This year's annual


B A R R Y wrote:

Do you taxi full rich?

We used to, which occasionally have us slightly low compression
readings on one or more cylinders in the hangar. The low cylinder
would move, as there was nothing really wrong. G We now lean
aggressively until we get to the runup area, and have never seen the
problem again.

Our home field is 250 MSL.


Can you (or anyone else) explain the mechanism of this? Why a full ruch
taxi would affect compression? I routinely lean the mixture for idle
and taxi because I've learned that at my home airport (KORL) the plugs
can foul between the ram and the run up area. But I don't understand
(and I'd like to be educated) how it affects compression.

John Stevens
PP-ASEL

  #25  
Old November 6th 06, 05:59 PM posted to rec.aviation.owning
Andrew Gideon
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Default This year's annual

On Sat, 04 Nov 2006 23:28:52 +0000, A Lieberma wrote:

I think that the high copper count doesn't necesarily mean anything
drastic...


It was the "significant change" from prior analyse that is causing
concern. The company faxed over the report and suggested to contact
Lycoming. The A&P feels the way you do, except to keep an eye on it and
get the oil analyzed again on the next change.


We just had a copper issue in an engine (O-360) about 200 hours past TBO.
Mattituck said "fly 15 hours and then retest". The A&P that contacted
Mattituck converted this to "don't fly the airplane until the engine is
overhauled".

Unfortunately, at least enough of my partners took the A&P at his word
regardless of the evidence I found to the contrary (none of which was
conclusive, I admit). They were all concerned that the bearings were about
to seize.

I'm certain that, had this engine been younger, the reactions would have
been more reasoned. But there's this incredibly strong belief,
apparently, that at TBO an engine should be taken out and shot. Even if
they do "know better" than this, the slightest problem is an excuse to
pull the overhaul trigger.

I'd be very interested to learn what the source of copper is in your
airplane's oil.

- Andrew

  #26  
Old November 6th 06, 06:05 PM posted to rec.aviation.owning
Andrew Gideon
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Posts: 516
Default This year's annual

On Mon, 06 Nov 2006 15:59:25 +0000, B A R R Y wrote:

coke up valves


I'm guessing that this doesn't refer to the Pepsi competitor. So what
does "coke up" mean?

- Andrew

  #27  
Old November 6th 06, 06:09 PM posted to rec.aviation.owning
pbc76049
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Posts: 28
Default This year's annual

Can you (or anyone else) explain the mechanism of this? Why a full ruch
taxi would affect compression? I routinely lean the mixture for idle
and taxi because I've learned that at my home airport (KORL) the plugs
can foul between the ram and the run up area. But I don't understand
(and I'd like to be educated) how it affects compression.

John Stevens
PP-ASEL


Not exactly the aircraft perspective you are looking for, BUT in recip race
motors
for sports cars, you do hot cuts if you want to read plugs or do compression
checks. This means you rev the motor to 4 or 5 grand, stabilize it and shut
off the ignition.
We find differences in the numbers we get just from excess fuel in the
cylinders with
idle cuts. Running at idle is a rich environment and the small washdown you
get can
make the numbers get funny on leakdowns. Another thing to consider is that
in
the trucking industry, idling loads the top compression ring gap with
sootlike
deposits that hinder compression sealing. It is something oil companys are
VERY
concerned about. So you now have 2 data points from very different places
that show you
that idling loads up the rings and effects the compression readings. YMMV

--
Have a great day

Scott


  #28  
Old November 6th 06, 07:12 PM posted to rec.aviation.owning
Jon Kraus
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Posts: 194
Default This year's annual

It's the heavy black carbon deposits that can build up on the valves,
piston crowns, ring grooves, etc... Nasty hard **** (technical term)

Jon

Andrew Gideon wrote:


I'm guessing that this doesn't refer to the Pepsi competitor. So what
does "coke up" mean?

- Andrew

  #29  
Old November 6th 06, 07:16 PM posted to rec.aviation.owning
A Lieberma
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Posts: 318
Default This year's annual

"pbc76049" wrote in
:

Not exactly the aircraft perspective you are looking for, BUT in recip
race motors
for sports cars, you do hot cuts if you want to read plugs or do
compression checks. This means you rev the motor to 4 or 5 grand,
stabilize it and shut off the ignition.
We find differences in the numbers we get just from excess fuel in the
cylinders with
idle cuts. Running at idle is a rich environment and the small
washdown you get can
make the numbers get funny on leakdowns.


Interesting you mention this, so we just may be able to get aviation
perspective in the next day or two.

I went to the airport this morning to see what was up with the corrosion
and found out that will be fine, but the cylinder with low compressions
isn't making the cut again after the leak test.

So, my A&P wants me to take it in the pattern, running full throttle when
I can for about 10 minutes and bring it back down for another compression
test. He is of the thinking that a high RPM will show a truer reading,
is my guess.

If the compressions don't come up, then we will have to send it off to
get it serviced.

I would have flown it today, but thunderstorms and small planes don't mix
too well, so I have to wait until this slow moving systme moves out.

Allen
  #30  
Old November 6th 06, 07:23 PM posted to rec.aviation.owning
nrp
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Posts: 128
Default This year's annual

I'm convinced compression readings vary with everything including
day-of-the-week and the phase of the moon etc.

My 172 M has (eventually) met compression for 31 years (I guess that
would be about 120 readings) but for about 10% of the readings it
required a retest 10 hours later to get a cylinder above 60, at which
point it would be back up. Through the years numbers though were
completely inconsistent except that the inconsistency was inconsistant
too.

I always used the same compression measuring rig (I called it the heart
failure model) so that was not the source of the variation.

John Thorpe preached that removing the upper spark plug before
compression testing could drop debris on any open valve faces reducing
the reading.

 




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