Hello, I am pretty new to quadcopters and i have a question. I have gotten everything hooked up and running I have an Multiwii pro flight controller. I downloaded the code from google. The problem that I am facing is when i go to run the throttle up and looking at the GUI all of the motors increase evenly up until 1220. At 1220 the rear left motor will stop increasing. All of the other motors will keep increasing steadily. Once the three motors hit a certain point the rear left will start increasing again, but it will be about 400 behind the other three. This leaves it underpowered and the other thing it wants to do is flip over. Here is a video i put on Youtube with a visual description of whats happening Click here. If any one has any ideas I would be more than happy to try them out. I have tried replacing the flight controller per the product support and it didn't help. Thanks for anyone who helps.
Hi,
Have you swapped motors around to see if problem is with a motor?
Have you got the same prop on all the motors?
Tom.... 
What happens if you move the platform slightly off level with motors at full throttle? Maybe the motor would pick up speed when the quad becomes airborne to maintain a level platform (assuming you have auto level turned on)
I have an Arduino. It's running some code I found somewhere. It doesn't do exactly what I want. What is wrong?
Have I paraphrased you correctly, OP?