Wednesday, August 10, 2011

Replacing the Motor and Gearbox in PZ UM P51

The motor and gearbox for Parkzone's Ultra Micro P51 can be easily replaced. If you plan on replacing both the gearbox and motor, you will need part# PKZ3624. The gearbox only is part# PKZ3527 and the motor only is part# PKZ3616. You can find a complete list of replacement parts for this aircraft here.

New Motor, Gearbox, Prop and Spinner From Horizon Hobby

New Motor and Gearbox Ready for Installation
To gain access to the internal components you have to take an Xacto knife and cut along the seam cutting through the decal on each side and along the rear of the top fuselage half.
Fuselage Access

Once you have access to the motor area you again take you Xacto knife and cut along the foam at along the areas shown in red below to separate the caulking used to secure the gearbox in place. You will also need to separate a couple of areas  of caulking that secure the wiring.

Once you have the gearbox, motor and wiring separated from the caulking, you will need to unplug the motor wires from the rear of the receiver. Note that the white wire is inboard and that the plug uses the out board two pins. Be sure to use tweezers to unplug the JST plug. Don't pull on the wires to remove the plug as this can break the wiring to the plug.

Photo shows the two pronged male plug removed from the reciever

Old Motor removed from the fuselage
At this point you will want to plug the new motor in and see that it runs with no problems. If so, lay down a layer of adhesive caulking along the fuselage sides where the gearbox mounts. Press the new gearbox and motor into this layer of caulk. Route motor wire along the side of the fuselage and under receiver circuit board. Plug the wiring into the the receiver and secure the wiring along the side of the fuselage with a couple of dabs of caulking. Also pull the motor wiring under the receiver to one side and secure it with a dab of caulk so that the wires are away from the aileron servo motor gear.

Put a second layer of caulking over top of the gear box flanges Allow the caulking to dry at least 24 hours before starting up the motor or putting any strain on the power system. The additional wires you see in the photos are for the navigaional lights that I added. The balsa cross members are an attempt to reinforce a badly deformed fuselage nose.

All that's left to do is put the fuselage top back on, secure it with a few pieces of Scotch tape and your motor replacement is finished.

Tags:Parkzone P51 Ultra Micro, RC, Radio Control, Airplane, Hobby


  1. Hi there. Nice blog. You have shared useful information. Keep up the good work! This blog is really interesting and gives good details. Planetary Gear Boxes, Reduction Gear Boxes.

  2. Thanks! Very helpful. I just finished replacing my motor to try to fix the pulsing it started doing, even with new batteries. The plane flies great now. Question: What adhesive caulk do you use? I used Gorilla glue, which foams up and then can be worked when cured.