When i look on The Earthshine Design starter Manual, there is a chapter about running one DC Motor. The book says i need 1 Transistor and 1 Diode, but i only have 1 of each.
So can i run 2 Motors with only 1 Diode and 1 Transistor?
Is your goal to make them both turn the same direction at the same time? Because if it is possible, that is all that will happen. I am not sure that the transistor they supply, though, would necessarily have the current capacity needed for both motors at once (without specs on the transistor and motors, you can't really tell). If it did work, you would probably need a good heatsink on that transistor.
If you want independently controlled motors, you will need a separate transistor, diode, and base bias resistor.
If you want to control the direction of each motor, you will need four transistors (and four diodes, and four base resistors) for each motor.
Its a bit coy on the specs for the motor, the one transistor may feed both but only in parallel, but considering the relatively low cost of a TIP120 transistor (5 for £3.00 here on ebay) and literally pennies for the diode, I wouldn't risk it.
Depending on what you want to do, two of these (one per motor) would allow you to run both motors independently and in different directions at the same time:
