did the third oil change in the IO-550 Legacy and here are
the issues I've had in the past 140hrs:

both front and rear tabs on the pax top AL baffle shelf (goes across #5
#3 #1 cyls) that hold the AL vertical baffle holder broke off.

cyl #5 is hottest, and is cooled better by cutting a hole in AL behind
the alt.  (get below the thinnest part of the cyl fins)

cyl #2 is next hottest, air is again stopped at the thin fins, this time
by the oil cooler box.  cut a hole in the oil cooler box so air can flow
around the cyl.

starter adapter slipped on hot starts and was replaced under warrantee.

oil vernatherm broke and was replaced under warrantee.

rudder cable to push rod assembly became sloppy and was removed and
rebuilt with more parallel surfaces decreasing 90^o offset free play.

rob logan bad modifications:

center tank vent issues

gap everything before paint... lots of gap, paint is thick!!!

com antenna switches impost an unacceptable line loss

remote oil filter on engine shakes too much.

cowl ram air blows / cools #4 and I'm not convinced the net effect was
worth the effort.

oil air separator into oil holder, overboard or into cyl head, remains a
question.

two 100 watt landing lights need big wires and +20amp breaker.

my electoral design overloaded the "second" alt, so I moved all lights to
the primary alt.

the new hyd pump (gear up in 3sec rather than 6sec) is very cool, but
required larger relays & wire.  (load is really 35 amps, even tough its
rated at 70 amps @12v)

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hot start is old news to most of you, but this is the process
I learned from an ovation driver and works well in the legacy:

cold:

push thr, prop, and mixture full forward..
high boost for 5sec
pull thr full back and then forward 1/4"
start (with cross tie)

hot:

push prop, and mixture full forward..
pull thr full back and then forward 1/4"
start (while slowly advancing the thr)
as soon as it fires: low boost
work the thr back to idle
low boost off

if failed to start, prime like cold, but only 3 sec

after 4 of above:

pull thr and mixture full back
high boost for 30+ seconds
goto hot start process.

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Utopian Maturity: Eternity, Liberty, Equality now Fraternity & Altruism.