RCGF 120CC-Twin Operator's Manual page 11

2. Once the location is established, use a drill press with a #5(.2055" / 5.21mm) drill bit as
a pilot hole. Once the pilot hole is established, use a 0.393"(10mm) drill bit to finish the
hole. In order to achieve a clean opening on both sides of the propeller, drill only half way
through the propeller with the finishing drill bit. Then flip the propeller over and drill
completely through the hole.3. Next, set the engine at the top of the compression stroke.
Note the position of the ignition magnet with engine inverted.
4. Place the propeller on the crankshaft at the one o'clock position.
5. Mark the location of one of the outer holes while the propeller is in the beginning of the
compression stroke position. Use a Dead Center Hole Locator to center and start the
hole.
6. Remove the propeller from the engine and drill the outer hole on the drill press using a
(.110"/ 2.81mm) drill bit as a pilot hole. Next use a 5mm drill bit to finish the hole. In order
to achieve a clean finish on both sides of the propeller, drill only half way through the
propeller with the finishing drill bit. Then flip the propeller over and drill completely
through the hole.