acroflyrgirl
Well Known Member
MX quiz.
A few weeks ago I did a runup and had a bad spark plug, or so I thought. Mag drop low on one mag, EGT hot. Taxi back, remove #3 bottom plug due to the EGT tip. Put in a new plug and the plane flew great....for the next 13 hours.
Last weekend, flew a few flights, all was well. 2nd flight on Sat. The engine began running rough. EGT's & CHT's normal but rough between about 2000 and 2550 RPM, smooth everywhere else. Mag check good at all power settings.
Took all the plugs out and #3 bottom was a bit wet with oil. Cleaned all plugs, installed and the run up was fine. Took off at full power, 2600 RPM all is good, then as I start pulling the prop back it did the rough running thing again. Smooth at 2600 & above, but rough still between 2550 down to 2000. Smooth as silk at 1900.
I did a cold compression check. All cylinders were 70 to 76, and I removed the oil filler stick/cap and heard a little bit of air.....on each cylinder. At first I thought ahh hah, but on each cylinder, with good compression. I guess that is normal?
The local IA, who is mostly a Continental 520 guy, asked me about my mags.
I have Slick mags with 970 hrs on them. I had some trouble with them earlier this summer and had the internal timing adjusted, but did not overhaul (yellow tag) both mags.
This local MX guy thinks it's a mag issue. Does that sound right in your opinion? I'm assuming the good compression eliminates a valve or a ring problem.
A few weeks ago I did a runup and had a bad spark plug, or so I thought. Mag drop low on one mag, EGT hot. Taxi back, remove #3 bottom plug due to the EGT tip. Put in a new plug and the plane flew great....for the next 13 hours.
Last weekend, flew a few flights, all was well. 2nd flight on Sat. The engine began running rough. EGT's & CHT's normal but rough between about 2000 and 2550 RPM, smooth everywhere else. Mag check good at all power settings.
Took all the plugs out and #3 bottom was a bit wet with oil. Cleaned all plugs, installed and the run up was fine. Took off at full power, 2600 RPM all is good, then as I start pulling the prop back it did the rough running thing again. Smooth at 2600 & above, but rough still between 2550 down to 2000. Smooth as silk at 1900.
I did a cold compression check. All cylinders were 70 to 76, and I removed the oil filler stick/cap and heard a little bit of air.....on each cylinder. At first I thought ahh hah, but on each cylinder, with good compression. I guess that is normal?
The local IA, who is mostly a Continental 520 guy, asked me about my mags.
I have Slick mags with 970 hrs on them. I had some trouble with them earlier this summer and had the internal timing adjusted, but did not overhaul (yellow tag) both mags.
This local MX guy thinks it's a mag issue. Does that sound right in your opinion? I'm assuming the good compression eliminates a valve or a ring problem.