When RC Helicopters are unbalanced they can literally shake themselves to pieces. Thus it is important to check the balance of all the rotor head components the moment you feel the slightest vibration.
All too often, pilots balance their main rotor blades and then start panicking because their electric helicopters still judder all over the place. They think something is seriously wrong with one of the electronic components. Yet most often, it’s just a simple matter of adjusting the flybar.
To see if the vibration is a flybar problem, remove the main blades and start the helicopter up (holding it securely) Now disengage the tail rotor via the transmitter control, so only the flybar is rotating. If the helicopter judders, 9 times out of 10 it’s the flybar.
All hobby grade eectric helicopters have flybar weights. These increase the stability of the craft and are adjustable - they dampen the cyclic the further out they are. When an RTF is delivered, it’s usually set up for beginner operation, with the weights right next to the paddles.
These weights can shake loose after a while, so slide them as far as they will go and restart the engine. If the heli still judders, it means there are discrepancies in the weight of the flybar or paddles. This is more common in cheaper built RC Helicopters. Play with the weights until you have eliminated all the vibration that you can.
As you get more proficient at flying, you can slide the weights inwards, or even dispense with them altogether. However, if moving the weights makes little difference to the vibration or performance of your aircraft, they are probably too light. In this case, you will need to resort to other methods.