Things You'll Need
Instructions
Remove the old gas engine from the plane.
Remove the parts associated with the gas engine, including the servo and push rods, fuel tank, fuel lines and fuel pump, if any.
Remove any balancing weights that were used, as the new motor, battery pack and ESC will cause the plane to balance at a slightly different point.
Determine the longitudinal center point of the aircraft, and make an indicator mark at that point. Find the COG balance point, and mark that as well. Normally, this is somewhere between the midpoint and forward edge of the wings. If you do not have a balancing jig, simply pick up the plane with one to three fingers (depending on the size of the plane) under each wing. Placement of your fingers from should be from a few inches to about a foot (again depending on the size of the plane) away from the fuselage. When it is balanced, it will be reasonably level from front to back.
Place the new electric motor, ESC and battery pack temporarily within the fuselage. The battery pack, as the heaviest item, should be placed as near the COG as possible. The motor needs to go as far forward as possible. Pick up the plane and again check the balance point. Move the various new components forward or backward as needed to come as close to neutral balance as possible.
Install the new components with double-sided foam tape for the ESC and battery pack holder. The motor can be mounted with either foam tape or screws, as indicated by the size and type of motor you chose. It is important to center the motor precisely from side-to-side for proper and safe operation of the propeller. Make sure neither the motor nor its ESC or battery pack interfere with any push rods or servos for operation of wing flaps, ailerons or elevator.
Double-check the balance once again. Any minor variations from neutral can now be fixed with the addition of balancing weights placed opposite the direction of tilt, i.e., in the nose if the plane balances tail-heavy; in the tail if it balances nose-heavy.
Consult the instructions that came with the new motor or consult your local hobby shop to determine if you need a different size or pitch of propeller than the original. This is quite likely.