Dirt Rag magazine calls it “the best mountain biking in the United States.” A Boston Globe reporter “felt like shouting ‘Wahoo’ like a kid.” The media raves are coming in about Kingdom Trails in East Burke — a huge, mapped, marked mountain-biking network in the Northeast Kingdom. About 90 percent of the pedaling paradise is on private land. Bikers come from as far as Maine and Ontario to ride the singletrack on trails called Poundcake, Todry’s Tour, Jaw, Beat Bog and — get this — Coronary Bypass.