Here are some steps to help diagnose the problem.
Note:
Lower rotors/shaft turns Left
Upper rotors/shaft turns Right

1. Check your locking screws on the upper hub and mid locking collar. Make sure that they are not slipping.
2. Check for bent shafts. Bent shafts can cause resistance in rotation.
3. Check Gear-mesh and gear teeth. Tight Gear-mesh also cause resistance, broken teeth will cause slipping.
4. Check your blades. Warped or bad blades will cause this.
5. Then reset your trim and proportional gain to the center.

Blades will cause this problem more then half the time. Make sure that you change and test different sets on the upper and lower. D@mn blades are always a trouble. Even after you check, boil, #match, balance and track they still sometimes have bad ones, and no two sets will every fly the same.

Here are some links to help you with the list above.

Quattro1975’s Bents Shaft Repair
http://www.rcuniverse.com/forum/m_6791546/tm.htm

Gear Mesh Guide
http://www.rcheli411.com/pages/howto.php?howto=7&page=2

Eat2muchrice’s Warped blade test
http://youtube.com/watch?v=_7PwNTXOWMs

Eat2muchrice’s Blade boil fix
http://youtube.com/watch?v=RmNv8OlG6GQ

RCFEIND’s Balancing Blades
http://www.youtube.com/watch?v=15h9G...eature=related


If it still does this then change out your bearings, if its not your bearing then change motors. I’ve heard of stock motors running over 400 flights. If you fix your problem and then your ready for more, check out this link.

Tips/Repair/Guides/Mods Links
http://www.rcuniverse.com/forum/m_68...tm.htm#6821632

Good Luck and Have fun.