Other Franklin Information

Bad running Franklin

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
jerryteits at comcast.net