This is a great tourer's route, not a 'sport' route, through beautiful and variable scenery. Most of Yelverton-Moor Gate (5 miles west of Mortonhampstead) is ideal, open, fast, consistent road with expansive moorland views BUT within Dartmoor's 40mph limit. And with good reason because farm stock wander freely (read mindlessly) and caused many serious accidents. A mate hit a dozing horse once and totalled his bike, the horse but not himself thankfully. Chill, sit back and enjoy. Take a break at Warren House Inn. Moor Gate-Exeter - a complete contrast. It's about bends, some very tight, and beautiful scenery. Road surface generally good but mud and gravel on some bends at times - especially after Mortonhampstead - a potential hazard. Not to mention bumbling grokels (tourists). If you're heading North from Exeter recommend you head up the A396.
This route I consider and adventure route - you can never go that fast dues to narrower country roads, car drivers not used to bendy bits, cows, ponies and sheep - but it is a great ride, one to savor and enjoy the journey and scenery and not the speed.
Plus Plume of Feathers in Princetown does a great pint of Jail Ale and for the missus Mortenhampstead has the fantastic Dartmoor Tea Rooms.
I would like to extend this review to the whole of the B3212 between Moretonhampstead and Yelverton. There are few bends, but the road rises and falls all the time. Speed limited, but with enough sheep around to keep your speed down in any case. The main attraction is the surroundings, which are striking on a clear day and on a misty one the ride is distinctly eerie. It is a good road for touring, but not for a blat.
My local run but taken in a circular route to include the road to Whiddon Down/ Tedburn st Mary/and back to Exeter. Can be bloody tricky when wet and during summer tractors dropping mud on the road watch for the grates in some of the bends
Loads of slowish corners through Dartmoor. Can sometimes have mud on road due to farm activity, but otherwise good.