The Black Knight - S1.E5

Split into episodes 10 and 11 in syndication:

The Black Knight

Mysterious Fires

Run time: 10 minutes, 42 seconds.

Gumby's playing with a giant electromagnet on a crane one day, which accidentally strips the armor off of a knight who was passing by. As they sort the mess out, Gumby learns that the knight is looking for someone who can challenge The Black Knight, who has placed a spell on the dragon that makes it burn down wheat fields. And so, Gumby confronts the Black Knight, who challenges Gumby to a duel over whether or not the dragon should be freed.