how can i fix my electrolux vitesse+reach vacuum?

When i turn my vacuum on it sparks like mad out the back of it from the motor and has an odd smell. Then the motor slows down and the vacumm goes off. When this first happened i had been using it on the hose picking up light crumbs. Now every time i turn it on it happens instantly. I have taken it apart to have a look at the motor but it looks ok theres no dirt in it its very clean. Ive had it 14 months and use it about twice a week.Its an 1800w. I am very handy with electrical repairs just need to know what the problem might be.