Is it easy to repair an electric lawn mower if you have some basic knowledge in electricity and mechanics?

I am trying to repair an old Black and Decker electric mulching mower, it works great for the first 10 minutes then the engine slowly dies out. I can re-start it and it will run for a few seconds then slowly die down until stopping. The engine gets weaker each time and the rpms die out. Any ideas as to the cause, the mower is more than 10 years old and if it's a matter of opening it up and replacing a transformer, capacitor or resistor I am willing to do it. Is it a problem on an interior circuit board or is it the engine that says I've just had enough. There are no burning smells, grinding sounds, nor is it making any abnormal noises, the blade is not caught and the mower has been cleaned regularly and well maintained. Any ideas as to repairing it or should I say farewell to it?