Peel sweet potato and slice them long ways very thin. I use my mandolin on the middle width blade. Drizzle with olive oil and make sure both sides of each slice is coated with the oil.
In a small bowl mix together chili powder, paprika and Cayenne pepper. You can use more Cayenne if you like more heat. Add a little cracked black pepper is desired.
Sprinkle spice mix over potatoes and rub on both sides of each slice.
Lay on med hot grill and cook on each side for about 10-15 min until done. Cooking time will depend on thickness of potatoes and heat of grill. Sprinkle salt on as soon as you remove from grill if desired.