Eco 7 Main Motor losing power

[rcpilot23]

After about 50 flights the main motor in my Eco 7 is losing power.

I have replaced it with a new main motor and the heli flys like new again.

Is there any specific way to service the Eco 7 main motor to restore full power.

I presume the communtator needs to be cleaned, but has anyone else attempted this with good results.

thanks