A regular 540 sized motor. I was running it today and suddenly it slowed down and stopped. I checked the 2S Lipo voltage and it is at 7.9V. I recharged the battery up to 8.4V and tried it again. the motor won't move anymore.

But if I push it a little, it will move a bit. It is a brushed motor, is it time for a new motor?

I took out the motor and notice that two green things got disconnected from one of sides.

ok, i soldered it back, but the motor still doesn't move

Those green things would be the capacitors, they help reduce radio interference from the sparks that you see sometimes. Though the greater problem would seem to be that the brushes in the motor are worn down to the point where they don't make good contact with the commutator. A new set of brushes and a comm cut and the motor should work like new.

man, i took the electric motor apart and i don't know how to put it back now. I forgot to mark the timing, polarity stuff, i think i will just buy a new motor.