Thomas Schmidt and Stephan Zaun from www.Aeroflug.de perform "on-wing" repairs to a Moki 400cc, 4-stroke, 5-cylinder radial engine installed on "Apache Princess" B-25 Mitchell. The camring gear is driven by two smaller gears which are driven by the crankshaft. Additionally, one of the two gears operates the impulse pump which provides pumping air to the carburetor fuel pump.

Access to the camring gear was gained by pulling the prop hub and removing the nose dome. It is unclear what caused the failure of these two cam drive gears. One possible scenario is that one of the gears failed and the other gear subsequently failed as it was unable to drive the cam ring by itself. No broken pieces of gear teeth were found which indicates that the teeth were simply ground down to fine shavings.

The camring drive housing was thoroughly flushed and cleaned, new gears installed and packed with grease. This section is only lubricated by grease. The crankshaft bearings,connecting rod bearings and pistons are lubricated by the 1:40 to 1:50 synthetic premix oil in the fuel via the intake section.