This tutorial is now complete. Report any errors to Divinderjit Singh Chattrath.
Hacking a servo with fixed angle of rotation and change it into a continuous rotation servo
Open four screws to remove the back cover pop out the electronics.

Front cover will also come off

The Gear assembly looks like this

The pin (as seen on the top of the left-most gear) stops the servo from moving beyond a point.

Take this gear out

Now our job is to remove the pin

Another method can be to file the pin off

We are good to go. Make sure the small bearing is in proper place in the case

and insert the gear n the top cover as shown below (orientation does not matter

Note that the potentiometer (Component marked as B502) is locked using four plastic locks

Open these locks. It does not matter even if you break these locks as we are not going to use them again

and the potentiometer can now be pulled out

we are going to de-solder this potentiometer from the board. Care should be taken in this step. Use of third hand is recommended.

Here is the removed potentiometer that we no longer need for this servo. You can use this in some other project!

and the board without the potentiometer

Solder two 1K resistors in series with a center tap and solder them onto the board as shown.

Press it down so that it is flat on the board but make sure it is not touching any other electronics on the board

Place everything back nicely

assemble the front and back covers with care and tighten the screws

You are done!