The Naseby Forest is a production pine plantation. Each time I've gone there everything has changed due to logging. Old trails close down; new ones open up in different areas... As of May 2017 the available trails were off Channel Road where there is a car park about 200 metres past the curling rink. There is a map board there to help you get started. A good bet is to ride up the Enterprise trail or Flushing Race which take you up towards the Ranfurly-Naseby Road. You could come back down on Fossicker or Roaches Gully. They are good if not inspired intermediate trails with less flair, scope and variety than the old trails in the area currently being logged. But things could have changed by the time you get there so check with the local information centre who may have a map. They'll certainly know which area are closed.