I have lost instructions for the v-max hypersonic helicopter and would like a replacement. Many thnx.

SOURCE: how do i replace tail rotor on v-max hypersonic copter

Depending on what you ordered for replacement parts. You can buy
the whole tail boom section or just the motor either way you'll need to
solder those hair like wires to the motor or the PC board. The motor just
slips out through the top of the plastic case that holds it. The hair like
wires route down the hollow tube to the PC board.

SOURCE: heli max hicro helicopter just keeps spinning in circles

Make sure you used the right blades, the top and bottom blades are different parts and if you try to replace an upper blade with a lower blade it will mess up the flight. The two sets of blades are reversed, the leading edge is on the opposite side because they spin in opposite directions.

If you are sure you have the correct blades, try to eliminate vibrations, especially in the upper rotor. Vibrations can throw off the gyro sensor and cause the helicopter to spin. If it isn't vibrating then you need to adjust the trim. If it is just a slight spin, you can try using the horizontal trim adjustment on the left stick. If this is not able to correct the spin, set the horizontal trim on the left stick to center and then remove the plastic canopy. On the circuit board you will see two screw adjustments labeled "SENS" and "SCALE". First, draw a mark on both of them with a marker making sure to touch both the screw and the plastic or board. This mark will be used to reset the knobs to their original positions if you mess up. The "SENS" (sensitivity) knob adjusts how hard the helicopter responds to the gyro. The "SCALE" (rotor scale) adjusts the balance between the two rotors. If it is a smooth rotation (as opposed to a skittish, jumpy, or erratic rotation), you need to adjust the SCALE knob as one rotor is consistently faster than the other. On the other hand, if it is erratic and jumpy, randomly spinning in quick bursts, you should adjust the SENS knob. Erratic spinning is a result of the gyro detecting vibrations and overcompensating, throwing the helicopter in a circle. Play with these knobs, try just slight adjustments and keep going until it flies right. Have common sense, don't turn the knobs too far at once, just small adjustments will make it easier. Also if turning the knob one direction makes it worse, go the other direction. If you turn the SCALE knob too much you may lose lifting power because it will reduce the maximum power of one of the motors.