[August 10, 2015]

I agonized all day Sunday over what could of caused the loss of power in the #2 cylinder on Saturday. There are three things an engine needs to run, and my #2 cylinder was missing one of them - compression, spark and mixture.

1) Spark - a missing ignition is very unlikely in one cylinder without affecting other cylinders in the dual ignition system I have.

2) Mixture - The only thing I could think of which could cause an mixture issue would be a clogged injector. Every time I have had a clogged injector before, I have always received a warning sign of high EGT's in that cylinder, along with a popping noise on high power settings. Neither of which I was experiencing.

3) Compression. Even though my compression on the ground was 78/80, it doesn't mean something didn't happen in the air which caused the compression to be lost. My thought is the most likely culprit is a sticky exhaust valve on the #2 cylinder. I started to disassemble the top end of the cylinder as much as I could tonight. First step was to remove the valve cover.

Next step was to remove the rocker arms by pushing out the rocker shaft. This was easily done with the piston all of the way at BDC. (FYI, I am more or less following Lycoming Service Instruction No. 1425A).

With the rocker arm shaft out, the arms came out easily.

The exhaust valve has a cap on it that us easily removed with a pick. Some people advise to use a post magnet to remove this, however, I have heard you should avoid using magnets whenever possible, as this could magnetize the material and cause ferrous metal in the oil to be attracted to it and cause excessive wear.

Next up was to use the "Rope Trick" in order to keep the valves from coming out. I quickly decided to use compressed air instead, as there are a few stories of the rope tying itself in a knot within the cylinder, and then you need to pull the cylinder to fix it! No thanks!



Last Modified: May 19, 2024