REFLECTOR: Franklin Cylinder Removal

Sat Jan 10 16:28:52 CST 2009

John, 

were the almost black plugs oily black, or powdery black? Same for the soot on the prop, is it oily black or powder black?? you called it soot, which makes it sound like powdery. That leads one to believe that (for some reason) those cylinders are runningrich. The half eaten away plug (firing poorly) can richen up that cylinder for sure. 

Keep an eye on things, and start with new, or freshly cleaned plugs. Then re-evaluate. 

My old & ugly cherokee 235 had compression levels that were just fine. The cylinders had Lots of years on them and almost 1400 hours. Compressions were all 75 or greater, but my oil consumption was higher than I liked. I burned 2 quarts on a 4.5 hour round trip. According to Lycoming, that was within specs. Some was leaking, some was burning. 

I noticed on one flight where I had to orbit at a search and rescue position for an extra hour (making the flight 5.5). that I had burned almost 4 quarts in those 5.5 hours. I had reached my limit and ordered cylinders. My compression was still pretty good really, but when I removed the culinders I found a broken 2nd ring on 4 of the 6 cylinders. The one that was causing me plug problems was broken in 6pieces!? The cylinders actually looked very good! The top ring was sealing at the top of the stroke where you take your compression reading. The wear and broken rings were NOT sealing as the piston traveled down the cylinder in the slight taper. This caused pressure in teh crankcase (blowby) which caused most of the little leaks. The oil was also slipping past the rings and burning. The top of the stroke was sealed enough so that most of the plugs looked pretty good (considering the hours/age of things). 

My point is, I think I wrang all I could out of those cylinders and it definately gave me a warning that something needed attention. After the cylinders were sent in, they actually still checked out within limits! at least as far as the bore goes. 
You might get by with just new rings, you might need new cylinders. It might be those finicky Franklin valves (make sure you have lead in your fuel!). 

Best of luck, and listen to your engine :) It may be giving you hints... but then they might be in polish too :0 

Kurt 

Kurt, Larry,  Thanks for the help.  Maybe the initial low pressure was due
to a stuck valve.  None of the bottom plugs had any oil.  However the EI
powers them and maybe the stronger spark burns the oil off.  2 of the plugs had
a light brown gray color which I understand is what it should be.  The rest,
including the one in question (#2) were almost black.  Also, center electrode of 

the #2 plug was half eaten away.  The rest were fine.  The oil consumption has 
gone from a quart every 3 hours to one every 2.  Also the soot on the prop is
darker, almost black.  Today I cleaned the engine so I can check for oil leaks.
I ran it for a few minutes and got 2 leaks from 2 of the bolts that hold the oil
pan on.  I removed the bolts and put some high temp silicone on them.  Guess 
I'll
fly it a little and look for more leaks.

John

--- lwcoen at hotmail.com wrote:

From: "Laurence Coen" <lwcoen at hotmail.com>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Subject: Re: REFLECTOR: Franklin Cylinder Removal
Date: Sat, 10 Jan 2009 11:24:18 -0600

John,

I agree with your mechanic that 73 is okay.  Before you pull a jug there a 
number of things you should do to make sure that it is necessary.  The best 
tool for examining a suspect cylinder is a borescope.  An educated eye can 
determine a lot about the health of a jug with this device.  Another thing 
that is a very useful indicator of ring wear are your spark plugs.  Oil on 
the lower plug is fairly common but oil on the top plug is a pretty good 
indication of worn rings.  Increasing oil consumption is another good 
indicator.  Kurt makes a good point about the possibility of a sticky valve. 
I think most Franklin valve problems can be traced to failure to lean during 
ground operations.  Listening for a hiss at the exhaust, intake and 
crankcase can tell you where the air is going.  In other words, find the 
problem before you try to fix it.

Larry Coen
N136LC
SE/RG Franklin/IVO

--------------------------------------------------
From: <aminetech at bl
uefrog.com>
Sent: Saturday, January 10, 2009 7:14 AM
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Subject: Re: REFLECTOR: Franklin Cylinder Removal

> Thanks Brian.  I'm aware of the manifold issue, but it's important
> and good that you mentioned it.  I'm rethinking to just redo the
> bad cylinder(s).  A compression test, with the engine warm, showed
> 75-80 in all but one.  The #2 initially showed 60.  The mechanic
> moved the prop and it went up to 73.  He said that was ok and to
> keep flying and checking it.  I'd appreciate any comments on this.
>
> John
>
> --- michalk at awpi.com wrote:
>
> From: Brian Michalk <michalk at awpi.com>
> To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
> Subject: Re: REFLECTOR: Franklin Cylinder Removal
> Date: Thu, 08 Jan 2009 09:24:29 -0600
>
> When reinstalling, you must torque down the intake manifold before
> tightening the attach nuts.  If not, you will crack your cylinders.
>
> If you have a PZL engine, the sleeves are of a different steel alloy.
> They are more difficult to replace and remove, but if your shop uses the
> proper procedure and tools, there isn't a problem.
>
> If you have any questions, the Franklin people in Colorado are pretty
> sharp.  It seems they are doing some volume these days.  Of course A-1
> in Jewett, Texas probably has the most experience.
>
> aminetech at bluefrog.com wrote:
>> Looks like I have at least one cylinder with bad rings, so I've
>> decided to have all the cylinder sleeves and rings replaced.
>> I've never removed the front two cylinders (# 1 and 2) and it looks
>> like there is not enough lateral clearance with the
>> engine in place.  Anyone know the easiest way to remove them?
>>
>> Thanks,
>>
>> John
>> ------------------------------------------------------------------------
>>
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