Same behaviour with my CX2 in the past, and had to change the motors. I too chose the XTreme 180 (you have to get an A and a B type motor)

CX2 parts here, including the Xtreme 180 motors (A and B):
http://www.xtreme-production.com/xtr...&Itemid=31

For the MCX, you will probably have to replace the 5 in 1:
http://www.e-fliterc.com/Products/De...rodID=EFLH1065

Gilles