McCulloch mt 700 weed wacker,the weed wacker will not spin to cut the weeds

If the motor is running another possible solution is you have a broken drive shaft spring PN-753-04280 To check this remove the screw which holds the **** pipe to the motor and loosen the clamp. The **** pipe should pull right off the motor exposing the end of the drive shaft spring. Pull the end of the spring, if it comes out it is broken.

If the motor is running, and the spool is installed correctly, this sounds like a clutch problem where the motor attaches to the spring that turns the head where the string is located. You fix this by removing the 4 screws that attach the motor to the pull string, separate, dismantle the clutch mechanism, replace. It is a good idea to service the spring as well with light grease, as this can get very hot and damage the unit. A clutch can go bad by having excess amount of string turning as well.