Honda 3818 starter issue

I have a Honda 3813, I pulled the engine and replaced the starter about a 1 1/2 years ago. Has run great till now. Now when I turn the key to start, I only get a buzzing noise from the starter solenoid. Some times when I turn the key I get the buzzing noise, and a spark comes from the positive post of the battery. I've checked all the connections. I've replaced the battery and starter solenoid, but still the same buzzing noise. I disconnected the solenoid and starter connections, ran a wire from the positive connection on the starter and touch the positive post of the battery, and the starter engages, and turns the engine over. Is this a starter problem, possibly shorting inside the starter? Any help would be appreciated.

Honda 3818 starter issue