The motor must be removed to replace the plugs.
Replacement
1. To remove the plug, drill a hole with a diameter of 12.5 mm for large plugs or 6.3 mm for small plugs. Screw a knob into the hole and remove the plug.
Small plugs can be knocked out, pry and get.
2. Clean the hole and press in new plugs. Expansion type plugs are pressed with the collar inwards.