The men at Walkera or other manufacturers might not do their job well that you sometime found the position of the Metal Gear attached to the  Motor is not perfectly matched the Main Gear of your helicopter. So you need this handy too for the use of removing pressed on pinions, it will save you a lot of time & frustration when it's time to change pinions.

Round Shafts (approx.):

• 1.86mm
• 1.73mm
• 0.90mm

Notched Round Shafts (approx.):

• 1.77mm (Round To Round)
  
• 2.78mm (Round To Round)
• 1.47mm (Notched To Round)
  
• 2.40mm (Notched To Round)

• Choose the proper thimble and install into the Rotary Rod of the Gear Puller, and lock the screw (note: don’t lock the thimble with flat step too tightly).
  
• Spin the Rotary Rod into the Holder.
  
• Mount the Removable Plate.
  
• Press the motor shaft in the Removable Plate, and move the shaft to vertically align the Thimble.
  
• Spin the Rotary Bar clockwise and pull out the motor gear.
  

If you have a Rotating Jaw Vise in your garage (it is just waste of money to ship from overseas because it is too heavy and the price itself is inexpensive so you better source it from a local warehouse) . You can use a Bearing (size to be a little larger than the metal gear) to push the Metal Gear on to the Motor Shaft easily. For example:

• 1 x Walkera Gear Removal Puller Kit