Takeoff 50 RPM less than before

[pauldan181]

The plan this morning was to stay in the pattern for a few T & G's as this was the first flight after condition inspection.
Runup was normal and the propeller cycled at 1800 rpm like always. I'm always aware of engine rpm after takeoff as I have the
Hartzell restriction to reduce rpm below 2600 "as soon as practical after takeoff". I have one Lightspeed ignition and one Slick mag.

Since final rpm adjustment during phase one 340 hours ago the rpm on takeoff has always been 2690 - 2700. Today during takeoff the rpm max was 2640. The annual inspection FWF was totally routine, plug clean and gap, oil change, air filter change, ignition
check, etc. The only change was I switched to Phillips 20w50 from Exxon 20w50. Any ideas why I suddenly have a 50 rpm drop from before? It was hot out this morning but the oil temp never got above 185 deg.

Aerosport O-360
MT Governor P-860-4
Hartzell BA

 

[lr172]

Could be a linkage issue. Before next take off, visually inspect the governor and ensure the arm is all the way against the high RPM stop/screw. If it goes back to 2700 on T/O, there must be a reason it is not always hitting the stop. During the CI, you could have bent the arm that holds the cable.

Larry