hi -

i recently bought a eflite blade cx2 from UK last week but i crashed it and now its not flying actually what happened was the upper blade was hit(minor) so i changed the blades but its still not flying the upper blade is not moving fast enough to lift the helicopter so can u suggest me something in this regard
thxz in advance
Digvijay mohan
9910036862

Are you sure it is ONLY the upper blade that is not moving fast enough ?  The chances for that happening are sort of rare, so please look at other aspects also. 

Unless you lost teeth in one of the two main gears, both blades should rotate at their designated speeds.  It is more likely as issue with battery power, or possibly even blade pitch angles (which can be adjusted using the linkage at top end of the main blade holder).

Here is an online copy of the manual for this heli (in case you don't have it).

http://www.hobbyzone.com/documents/EFLH1200-manual.pdf

Also, note that these coaxial helis have the two sets of blades rotating in opposite directions.  So when you fixed the replacement blades (the top ones), make sure you aligned them for the right direction of rotation.  The leading edge of the blades should be towards the direction of rotation.

If when you give Throttle, both set of rotors start to turn? (but you said the upper is slower) then give right or left Rudder and see the variation in the speed. You cab try the same with adjusting the Rudder Trim. You also might be able to set this on the receiver, there are 2 small parameters that can be altered to fix this. But please remember GO STEP BY STEP in eliminating the problem, do not touch the gain unless you are sure.