Candy Aquaviva 800 / Abise 650

Hi, I have 2 candy washing machine Aquaviva 800 / Abise 650 with the same problem, when you put a normal load in they do not turn, but it does spin at the end. if you take out most of the things it does go normaly. it seams that the motor is to week to turn it. it makes that noise when the motor is on but does not move. than when you put it for a spin..gradualy it does get the speed and it goes..what do you think is the problem..
thanks