I have a "Toro 14 inch cut super heavy duty trimmer," it's about 20 years old though lightly used until recently. My mom's yard is tiny, so I've been cutting it with this. This last time, it seemed to be running at half power, then would slow and stop, and emit a "hum". I'd let it sit for a few hours, and turn it back on, and it would cut, though at about half power again, last a few minutes before stopping and the hum starting again. I'm curious if I've just fried the motor, or maybe there is a fix for this? Thank you for any suggestions.