Rotax A Drive Gear Box Drive Removal Procedure for Rotax 377, 447, 503 and 532 aircraft engines.

Tools Required.
13 mm socket
17 mm socket
Ratchet
Allen wrench
Propane torch
Hammer
Oil drain pan
Rotax reduction drive gear puller
Johnson bar
12 inches rope
Spark plug wrench 

 First drain the oil from the gear drive assembly, using a 17 mm wrench to remove the drain plug from the bottom of the gear drive. With a ratchet and socket/wrench and loosen the six, 13 mm nuts, retaining the drive to the adapter plate. With all the nuts loose remove the top 4 nuts and washers in a gear down assembly, or the bottom 4 nuts and washers, in a gear up assembly.

Grasp the drive by the output shaft, and pull outwards on the drive. On older model drives it may be necessary to turn the engine over while pulling out to allow the gear to clear the gear oil slinger
This slingers no longer used and should be discarded.

With the drive removed it is next necessary to remove the adapter plate. To allow access to the 4 allen head screws securing the adapter plate to the gear drive, it maybe necessary to remove the 4 studs (#3, #4 & #9 in diagram on right) used to hold the gear drive to the adapter plate. 

To do this screw one of the 13 mm nuts removed from the studs onto the stud, until it is near the bottom of the threads. Now install another nut onto the stud until it locks against the first nut. Now using 2, 13 mm wrenches tighten the nuts against each other. Then come in and using a 13 mm wrench remove the stud, by turning counter clockwise on the first nut. 

Repeat for the remaining studs as necessary. 

With the studs removed, use a hammer and sharply wrap each of the allen head retaining screws. This will help shock them loose from the Blue Loctite used to help retain them. Before attempting to remove the allen screws it is suggested that you use a propane torch or B tank to heat the crankcase, in the area of the threads holding the bolts.

With the bolts shocked, the crankcase thread areas heated, use an allen wrench to remove the four retaining screws. If you strip the heads of the screws, use a pair of VICE GRIP style pliers to grab the outside of the screws, to aid in removal. 

Tools Required Tools Required
17 mm socket
Ratchet
Rotax gear puller
12" piece of rope spark plug wrench

Gear Box Removal Procedure
Using a spark plug wrench remove the spark plug from the PTO side cylinder. Turn the engine over clockwise until it is past TDC and the piston is positioned about 1 inch down in the cylinder. Take your 12 inches of rope and feed it through the spark plug hole until 8 inches or so are located in the combustion chamber.

Turn the engine over counter clockwise, until it locks up. Place your () mm socket onto the bolts retaining the gear to the crankshaft. Using a Johnson bar turn the socket counter clockwise until the bolt comes free. Remove the bolt, washer, and impeller, if so equipped.

With the bolt removed, remove the rope from spark plug hole. Turn the engine over until the PTO piston is at TDC. Rotate the crankshaft counter clockwise until the piston is approximately 1 inch down in the cylinder. Again install your rope. Bring the piston up until the engine locks up.

Install your Rotax gear puller into the threaded section of the gear being sure to thread the outer puller half of the puller all the way in.

Install the puller bolt in until it butts against the crankshaft end. Install a socket onto the end of the puller bolt, then using a Johnson bar turn the bolt in a clockwise direction until the gear comes free of the crankshaft.