I see... I know servo testers exists, thought it was the same with motors. The thing with the quattro is, its not like 250 quads or other quads with brushless motors... To test them out by changing them one by one can be a really big job. What Ill do is prolly prepare a strut with a motor already mounted and change the struts one by one to see if it fixes my problem. So then Ill know exactly which motor is running out. The thing is I think theres counterclockwise motors and clockwise motors so, I may need two struts with motors mounted, right ?