Step 1: Parts list and Tools
1 - 1-9/16" length of .04" (or 1MM) carbon fiber rod
2 - 1x3x1 ball bearings (item Code m021 from http://www.precisionheli.com)
1 - Picoo-Z mini Helicopter
The tools required are;
small dental pick
a standard (flat end) screwdriver
a pair of locking needle nose pliers
a pair of diagonal wire strippers
1/8" drill bit
a large flat washer (I cut a small 1/8" deep slot in it to help remove the rotor)
Foam Safe CA glue
and a good magnifying glass will help too
Step 2: Opening up the body
Next start cutting through the seam that runs all the way around the copter holding the 2 halves of the body together. I started at the the back where the tail rotor arm runs into the body (less delicate stuff in this area). Once you get it started you can pry it open slightly, so that you can see what you are doing, (to stay away from the wiring and battery, to get the two halves separated all the way around.
Once I had this done, (see 2nd pictures), I switched it on and ran the copter at low speed to makes sure I hadn't broken anythings up to this point.
NOTE: From the 2nd picture you can see why a push-pin (mod to add weight) in the nose of the copter could be a bad idea. It's close to the battery compartment, and a crash could drive the pin into the battery.
Step 3: Removing the Main Rotor
Step 4: Removing the drive gear and bearings
Step 5: Cutting the Carbon Fiber shaft
Step 6: Installing the new shaft & bearings
Step 7: Re-installing the Main Rotor
Step 8: Glue it back together
Check again to make sure the main and tail rotor are both working before continuing.
Next apply some glue carefully around the two halves of the helicopter body and press it back together and secure it with some rubber bands. You can also glue the "Landing gear pod" back in place as well. Now let it set until the glue dries (following the instructions for whatever type of glue you are using, just make sure it is Foam Safe).