Hi Talontsi96, welcome to the cursed world of heli vibration. Of all the things that I've dealt with in this hobby this is the one problem that drives me crazy.....ya know what I mean??? The main rotor shaft should be very straight.......some guys check it by rolling it on glass. The last vibration that I had was probably due to an "ever so slight" bend in the main shaft. I say probably because I also replaced the crown gear.....and upon reassembly the vibration was mostly gone. As far as the main shaft goes.....using a flat glass surface to see where and in which direction the bend is.......you can carefully apply pressure in the opposite direction to correct the bend. Also the m.r. hub can cause vibration. It's all so tedious! But once you get the problem corrected....... the other aspects of the r.c. helicopter hobby are great fun. Mark