I suspect that the fault lies with the tube (I am assuming you mean the long flexi-tube )rather than the motor. If there is some damage in the tube this can cause it to flatten, especially if it has been overstretched or kinked....
I would check this out first, it is much easier and more cheaply replaced than a clutch or motor assembly as well as being a more likely cause of the problem.
Mark, June 2005
