a. Is the motor greater than 25 horsepower? If the motor is greater than 25 horsepower, the first step would be to price a new motor, and compare it to the quote from the motor repair facility. If the quote to repair is 80% or more than the cost of the new motor, then it is better to purchase. History does play a part in this, as the experience with the motor shop weighs heavily in this decision. However, at 50% of the cost of a new motor or less, it is always better to repair than purchase. Good repair shops use VPI to prolong the life of an armature, and insulate the heat.
b. If the motor is less than 25 horsepower, it generally is better to purchase a new motor, with a warranty. However, there are some repair shops that specialize in small motor repair and stake their reputation on the quality of their work. It pays to investigate, if you have the time to do it. Due to the volume in industry, there is little time to devote to this task other than concentrate on replacing motors less than 25 horsepower.