Sounds like maybe you didn't peel it? I get the stronger peppery/resiny flavors from the skin. I actually like it, but apparently a lot of people peel yacon to get rid of that.
I've also heard that they are stronger tasting when grown under drier conditions, but I can't test that myself.
Sunlight usually sweetens them up some.
I harvested a couple that I wanted to save to produce seeds before this weekend's wind storm (and, sure enough, it shredded the rest of them).
21 lb from 2 plants, leaving a couple pounds of storage tubers attached to the crowns to feed them in storage.