REFLECTOR: Help with poor running Franklin

[Chuck]

Jerry, assuming that you have good mags, proper timing, the correct carb, 
etc., it sounds like you might be getting poor ring seating probably due to 
altitude. At 8,500 ft, the density altitude will reduce the horsepower by 
about 40% which reduces cylinder pressure thus not allowing the rings to 
seat, especially if you're running the engine rich (gas acts as a lubricant) 
which is very common. The excess oil and gas will quickly foul the plugs, 
and you'll get missing, and thus the engine won't rev up. The first place to 
check is the plugs to see which cylinders are darkest. I suspect you'll find 
a couple which are very dark around the electrode, maybe even wet. The bad 
cylinder(s) will be very cool compared to a firing cylinder. Carbureted 
engines are notorious for uneven mixture distribution, particularly at idle. 
If you have the wrong (too rich) carb, you'll notice that when you lean it, 
it takes a lot of movement to get it to lean and with just a little more 
leaning it will quit. The oil will turn back quickly as well.

If this turns out to be the problem, I'd suggest the following:

1. Invest in an individual EGT sensor measuring system, if you haven't got 
one which will immediately tell you which cylinder is not firing.

2. This may sound extreme, but I'd take the engine off the plane and send it 
to a (preferably, low altitude) A/C engine rebuilder to see if they can run 
it until the rings are seated (break it in). I did this with my engine 
(IO-360) and they found a few things that were wrong (timing, etc) which 
they easily fixed. They ran it and gave me a spread sheet of all the 
parameters (hp, oil pres, EGT/CHT, etc), and the cost was under $1,000.

I used Bart at Aerosport (205-376-2955) in Kelowna BC who is a great guy and 
really knows this stuff, including having a good engine test facility. Worst 
case, you might have to rehone the cylinders which he could do (if he'll 
work on a Franklin). I drove up from Seattle to pick up the engine at his 
shop and watched them do the testing. I really learned a lot from this. 
You're a lot farther away, so maybe there's somebody closer (at lower 
altitude) that you can use. I originally shipped the engine to him which was 
easy. I'd give him a call to see what he'd suggest.

3. If you still want to fix it yourself, you could try the following:

a. if the plugs are fouled, run a hotter range plug for break in. You'll 
need to tie down the plane so you can run the engine up to 2,000+ rpm to get 
enough cylinder pressure to seat the rings

b. change the (using mineral oil?) oil if it's black, and refill with a few 
quarts less, so there's less oil to blow by the rings.

c. aggressively lean the engine to get the heat into the cylinders, but 
don't exceed max mfr recommended temps. You'll need to shut it down and let 
it cool between runs. An engine test stand has a prop blowing air over the 
cylinders so that they stay within range.

Basically, you're just trying to seat the rings which is critical for long 
engine life, and that takes cylinder pressure and temp to accomplish this. 
It's really important to have a good, reliable engine if your flying around 
mountains. Good luck.

Chuck H







--------------------------------------------------
From: "Brian Michalk" <michalk at awpi.com>
Sent: Thursday, March 26, 2009 7:35 AM
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Subject: Re: REFLECTOR: Help with poor running Franklin

> Excellent suggestion.
>
> Comment on the timing.  For a new installation, take it easy on the 
> timing.  The Franklin is spec'd for 28 to 32 degrees of advance.  Breaking 
> in a new engine, or cylinders results in higher temperatures.  Retarding 
> the timing a little will help you manage engine temps if you are having a 
> hard time keeping your temperatures below redline.
>
>
>
> Yahoo wrote:
>> Hi Jerry,
>>
>> Cylinder compression test results? I had a foreign object caught under an 
>> inlet valve - looked to all the world like a fuel problem or induction 
>> leak (sticky valve might do the same thing).
>> The leaky valve was causing the induction manifold to loose vacuum 
>> (Cylinder was pressurising the inlet manifold) and when that happens, 
>> fuel doesn't get sucked out of the Carbie, engine didn't quit - but big 
>> loss of power.
>>
>> Have you tried leaning out really hard (on the ground, almost til it 
>> quits) for 2-3 minutes?
>> /*It is fairly non-reactive to mixture changes*/. sounds a bit weird?
>> The only backfiring I've experienced was due to ignition timing - you do 
>> have your Franklin timed at (from memory) *32 *degrees BTDC right?
>>
>> Q: Does this poor performance happen all the time or only occasionally 
>> like whe the engine is hot?
>>
>> Hope this is of use
>>
>> Steve
>>
>>
>> Jerry Teitsma wrote:
>>> Please help me with your ideas for my dilemma.
>>>
>>> I have flown my Velocity Elite FG for 26 hours but the engine has never 
>>> run well.  I have attributed that to oil blow by that has frequently 
>>> fouled plugs.  The rings did not seat at least partially due to the high 
>>> altitude where I fly (8200 ft. field and flying at 10,000 ft or more as 
>>> well as the hard steel cylinder linings. As a result, I recently pulled 
>>> the engine and did a top end overhaul with new softer cylinder liners. 
>>> It now runs even worse.  I can't get more than 1500 rpm although it 
>>> idles fairly well.  It cuts in and out with back firing intermittently. 
>>> It acts like it is starving for fuel or has induction leaks.  It is 
>>> fairly non-reactive to mixture changes.
>>>
>>> Following is a list of items that have been done in chasing the problem:
>>>
>>> 1.  I plugged the exhaust pipes and pressurized the intake manifolds to 
>>> about 15 psi using soap to look for any induction leaks.  I found none.
>>>
>>> 2.  The MA-5 carburetor was removed and sent in to a test shop where it 
>>> was checked for flow rate and a service bulletin 13 was performed.  It 
>>> tested out OK.
>>>
>>> 3.  The fuel flow rate was checked and found adequate in fuel flow and 
>>> in pressure.
>>>
>>> 4.  The mag timing was checked and rechecked and is right on.
>>>
>>> 5.  The mags were taken off the engine and checked for correct action 
>>> and timing.
>>>
>>> 6.  The wiring was traced through for the mags to the cylinders to make 
>>> sure they were not cross wired.
>>>
>>> 7.  The spark plugs (nearly new) were removed, cleaned and gaped.
>>>
>>> 8.  We removed the valve covers and checked the open and closing 
>>> sequence of intake and exhaust valves.  All seem to occur at the correct 
>>> time and in the correct overlap.
>>>
>>> The only thing we can think of that has not been checked is the cam for 
>>> proper lift and timing.
>>>
>>> Although it has never run well, it has run better prior to the overhaul. 
>>> Has anyone experienced similar problems?  Any ideas?  I would really 
>>> appreciate your input.  JT
>>>
>>> Jerry Teitsma
>>> PO Box 796, Granby CO 80446 (USPS mail/shipping)
>>> 36 Lodgepole Ct, Granby CO 80446 (UPS/FedEx shipping)
>>> 970-887-3910 (Phone/Fax)
>>> jerryteits at comcast.net
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