Eliminating vibrations
The first thing is to assemble the machine. Next you will take some of it apart.
1. Take the main blades off, take the tail blades off, and remove the flybar assembly from the rotor head.

2. Now turn on your radio and plug in the battery. Hold the machine in your hand and run it up. It should be very smooth and quiet. If it is not, find and correct the problem.

3. Install the tail blades. Now the next part is up to you. You can run the machine up on The ground or USING EXTREME CAUTION and ALWAYS WEAR SAFETY GLASSES hold it in your hand by the landing gear and run it up to RPM again. What you are looking for is that the output tail shaft is dead true and smooth running from stop to full rpm. If the shaft vibrates are appears to move up and down you have a problem. Look very carefully at the gap in-between the tail blade grips and the tail hub. They need to be equal when you pull out on the tail blades. If they are not, you need to trim the longer screw some. If the tail is not smooth after that, then swap tail blades and see if the problem improves or gets worse. At this point you will have the tail blades on in the smoothest location but you may still have a vibe. Now you need to go get some scotch tape or clear packing tape. Start with a small about, maybe ¼ inch and attach it to one of the 2 blades about ½ of the way out. Run up the machine and see if it is better or worse. If it is better then adjust the tape amount to get it 100% smooth. If it got worse then try the other blade and do the same. Using that technique you should be able to get the machine very smooth up to this point.

4. Next install the flybar assembly and the linkages. You will now need to run the machine up and check for vibes. Use the same process as the tail blades to get a smooth running machine.

5. Now for the last setup, installing the main rotor blades. NOTE: it is VERY important to run the model up on the ground in normal mode with very little or NO negative pitch. If you have negative pitch you are risking a boom strike.

By using that vibration elimination technique you can isolate problems and you really know where the problem is as you are working step by step. If you try to eliminate vibes when the machine is fully assembled, you are just chasing your tail. Use a methodical method and you will fix your problems much faster and more reliably.


Source: summary of important information from different internetwebsites