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According to the logs, they were cleaned and gapped at annual about 20 hours ago.

Good point. I'll pull the cards and look at the data next time I go out to the airplane.

Hey All, Looking for some advice. My 92 M20J MSE has an overhauled engine and dual mag. I have noticed a few times on run up that the right mag drops a lot more than the left. ~70rpm more. It dropped today from 2030 to 1830 which is obviously higher than what is on my checklist. It runs smooth on both left and right. I do use pretty aggressive ground leaning. In the few cases I had an excessive rpm drop, I went to full power leaned out and stayed there for a minute or so before trying the runup again. Everything alway checks out during the second runup. Plug fowling is the obvious first possibility, but I thought I had eliminated that with aggressive ground leaning. Recently I have leaned so much that I had to richen slightly to make more than 1200rpm when pulling out of my spot. Are plugs just fowling or is there something else going on I should be thinking of? Thanks all

This happened to me. Trim switch on the yoke was backward after my avionics install. Luckily I recognized it was backward with just a few seconds of trim input once airborne. My mistake was checking the trim on the ground but not checking the direction. Lesson learned.

Thanks for the reply. Fair point on the order of operations for shut down. Checklist calls for master off first then alt field. Sometimes I inadvertently reverse those steps. I did just have the voltage regulator overhauled and this was happening before then also, so I don't think it's related to voltage regulator. Good to know this is common. My A&P didn't seemed concerned (it's a standup outfit, I trust them), but I wanted to understand it a little better.

There are a couple issues I wanted to get input on from the hivemind. Frequently, if I turn off the Alt field switch with the master on, the alt field breaker flips. It does not flip when I turn off the Master first. I have noticed a burble in the engine rpm once the engine is hot on the ground (need to confirm if it doesn't happen when engine is cold, but only noticed it so far after landing and taxiing). Every few seconds, engine will decrease 10-30 RPM and then go right back to where it was before. I might not have even noticed if not for the digital RPM readout. I can also hear it slightly in the headphones. Still happens even if the engine is very leaned out for ground ops.

Over due update. Had my first annual and a lot of other work done. Here's what I've had done so far since I got it Overhauled engine New prop New oil hoses / oil cooler Overhauled prop governor New scat hose Fixed brakes by rebuilding / replacing fluid Replaced baggage door and cabin door seals Second oil change New avionics panel New locks (baggage door lock was inop so replaced both locks with medco) New alternator Overhauled voltage regulator (was running hot at 30v) LED landing and taxi lights New battery (with engine reinstall) New stall switch I am sure there are more things that I missed.

Wanted to provide an update on this. Shop found significantly over due brake fluid which was likely the culprit. Described the consistency as like honey. Here was the work done to get it working like new: Rebuilt all master and slave cylinders Replaced brake pads Replaced brake discs with Black Steel Flushed fluid fully (removed all fluid and replaced with new) Bled brakes 2x (first time pedals were mushy, second time worked like a charm) Brakes are now very effective.

Overdue update. Shop fixed RPM sensor and it's dead on now. They commented they are using a p-lead based sensor. I did get % power to show, and calibrated the fuel flow. It looks a lot closer now than prior. Engine has ~27 hours now. Airplane has been flying pretty good. Getting her flying at least 2x a week at this point.

Was there any wind during landing? I've noticed a gusty cross wind that kicks up after landing can sometimes cause me to need to react quickly with the rudder pedals to prevent a runway departure. This mostly appears to be related to slop between the nose wheel and rudder pedals. I'd check to see if you have any slop either between your rudder and pedals or pedals to nose wheel. Might be illuminating.

Just wanted to add that I came back to this after the fact and agree with you 100%. It would have made a lot of my progress a lot easier.

I might need to look at the calibration. I'll try one more time first though when the RPM is working properly and set it exactly to book numbers (including mixture) / check the fuel flow. Interesting on % power, I hear it's in the config. I'll ask the avionics guys. That would be even easier than a key number for sure.

~20 hours on the engine. So yes, thats a good point. It's not done being broken in yet.

Good tip on key numbers, I just read about them as a result. I like the concept. Makes power management a lot easier. I am currently running it full out for break in. I did have the prop back to 2600 roughly but with the inaccurate RPM decided to push it up to 2700 for the picture so that I could compare TAS and power setting to POH more easily later. I was just a little surprised that the indicated airspeed wasn’t higher, but looking at the book + historical photos in cruise that is the same speed I was making prior to avionics install. So it checks out. I was just able to dig up this photo I took prior to the install. Everything looks identical except RPM and Oil temp. Hopefully those are resolved. I plan to pickup fly her again next weekend.

Oil temp probe was replaced subsequent to this. Oil pressure was also turned up subsequent to this. Good point on the CHTs. What would you expect for that fuel flow? Cowl flaps were closed fully FWIW. I landed once I realized Oil temp was probably incorrect.

Thanks! RPM sensor is malfunctioning in this pic. Prop is set to full forward though (2700RPM). Throttle is also full forward (still in break in period). I am running a little rich (127ROP) need to run it leaner.

Been flying a bit, but been working on the list of squawks (down to the last two now). This airplane sat for long time before I had it and I've been slowly dealing with all of the issues. Question for the group. How does this look performance wise. I know the RPM sensor is off (it was fixed after a second visit back to the avionics shop). Prop is set for 2700rpm in this photo. Airspeed seems a little low to me, but looking at the POH the TAS is 6kts under. Fuel flow also seems a little high. What does anyone who has experience with this model think? I just don't have a ton of experience with this airframe, so hard to know that is normal. I was expecting closer to 155kias from my limited experience prior to the avionics upgrade.

The shop is just about done with the corrections. To the point made earlier, the RPM sensor has been a bit of a problem. They were only able to get to ~100rpm of the measured value. Good news I didn't share earlier: Useful load is now 1039lbs. Net removed ~50lbs of stuff from the airframe. It was really hoping to get useful load over the 1k mark. Now it's firmly there.

Its interesting, I wonder how this is supposed to work. Usually with halls effect sensors you have a magnet mounted to the spinning part you want to measure RPM of and then the sensor mounted to something fixed near by (in this case the magneto case). It's usually pretty straight forward unless there is a lot of EMI nearby. I wonder if you lost your magnet or if the engine bay is a particularly EMI rich environment. I can imagine a magneto would throw off plenty of EMI.

That doesn’t sound fun. RPM is pretty important. Hopefully mine is easier.

Welp, hopefully they can get it fixed quickly. The more you know, right?

Looks like the shop will take a look at it again this week. Hopefully more bleeding as suggested will take care of it.

Good question. I didn't have the sense to check it when I was there. Shop is taking a look today. I'll let everyone know what they find. I did notice some fluctuation on the RPM value while on the ground a few times. Might be a bad / loose sensor.

It's something similar to this. A&P showed me one time in the shop. https://www.pilotshop.com/catalog/inpages/jpi10-05459-61.php I believe it works on halls effect.

Right side speed brakes. Left side is quiet. There is only 1 RPM reading. Settings were set to 2600 RPM and engine sounded like 2600 RPM. Plane climbed well also, but RPM read only 2270 I will definitely make some adjustments at some point, there was just enough that I sent it back to the shop.