REFLECTOR: Bad running Franklin
Jerry Teitsma
jerryteits at comcast.net
Mon May 4 08:53:06 CDT 2009
Several of you have helped me search for a solution difficulties in getting
my Franklin engine running properly. As a brief recap, I bought the PZL
Franklin new about 5 years ago and flew it for about 26 hours. It never ran
well which I attributed at least partially due to plug fouling. The rings
never seated properly. I finally decided to re-sleeve the cylinders to get
a softer grade of steel as liners. I sent the cylinders to Davis Aviation
for new sleeves. I fly out of an elevation of 8200 ft and it is difficult to
get manifold pressure.
After reassembly of the engine and re-installation, the engine ran worse
than ever - back firing and popping and difficulty getting RPMs above 1500.
I checked everything - induction leaks, carburetor function, mags, wiring,
plugs - you name it - nothing helped. I tried to locate centerline intake
valve angle but had difficulty locating these number. Eventually, Phil
Davis of Davis Aviation located these numbers and sent them to me.
Saturday, mechanic John Welty and I used these numbers to check the center
line angle for the intake valve on #1 cylinder and found the angle to be off
6 degrees. Instead of 104 degrees, the angle was 98 degrees. So, the
engine was pulled once again. We took off the mags and accessories at the
back of the engine and took off the rear cover. Then, we pulled the starter
ring, revealing the cam gear and crank gear.
When rotated, the mark on the crank gear meshed between the two marks on the
cam gear (or the other way around) just like the book said it should but the
center line angle was wrong. We pulled the crank and cam gears and reset
them so that the angle was correct. We had to move the gear one tooth -
about 6 degrees.
After reassembly and reinstallation, we started the engine and it now
appears to be running well. I have not yet flown it but intend to do so
this week. It has been a frustrating - and expensive - several months
trying to get this resolved.
I'm not sure why this happened but have a guess. It appears that the cam
gear or crank gear was miss-marked. When the engine was test run at the
factory, it likely did not run at all well. It appears that they opened the
valve lash enough to run. When we reset the valve lash to the proper
amount, the engine would not run. Now that the cam timing is correct, it
runs with the proper valve lash. Sounds incredible but I can't think of any
thing else.
If anyone needs or wants a copy of the valve lift versus angle, please
contact me and I will e-mail the table to you. Thanks to each of you for
your suggestions and help.
Jerry Teitsma
Granby CO
970-887-3910 (Phone/Fax)
jerryteits at comcast.net
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