Worn motor brushes, a faulty drive motor or using an improper extension cord can cause slow motor speed.
Using a long or lightweight extension cord causes a power drop, which decreases motor speed and results in the blade spinning too slow. For a 120-volt table saw plugged into an outlet protected by a 15-amp circuit breaker, extension cord length typically shouldn't exceed 25 feet. Use a shorter or heavy duty extension cord that can handle the current draw of the table saw so the motor spins at the right speed.
Worn carbon motor brushes can prevent the drive motor from running at full speed, so inspect the motor brushes. Replace the motor brushes if they're worn.
If the motor brushes are okay, then an internal motor failure may prevent the motor from spinning the blade at full speed. The motor typically overheats when it has an internal failure. Replace the motor if it overheats and doesn't spin the blade at full speed.
