Have you checked the national forests? Like Uwharrie,
Nantahala,Pisgah (mtns) Croatan (east) ?
Uwharrie would be closest. I think all of those have atv trails.
Uwharrie
NCNatural's Uwharrie National Forest - Trails
link to national forests. Trail maps etc.
National Forests in NC Recreation (http://www.cs.unca.edu/nfsnc/recreation/recreate.htm - broken link)
Sorry, used to be lots of trails in this area, but they are pretty much either developed, private property, or motorcross tracks now.