The start of this trail is a little hard to find, but it is very close to the Buck Mountain Campground except that it is on the other side of the creek. When the creek is low you can start from the campground otherwise you'll want to cross the bridge over Johnson Creek and head to the official trailhead. The trail is accessed from FS414C.
This eight-mile trail is a nice, remote experience since it traverses near the boundary with the Frank Church-River of No Return Wilderness. The trail traverses above the creek over its whole length and does get faint in sections. Early season there can be a lot of downfall, but it usually gets cleared once a year.
At the end of the trail you'll find yourself crossing Johnson Creek, which can be deep so beware if you ride this trail in the early summer. Or you can just do the trail as an out and back and skip the last downhill down into the creek. You can do this ride as a loop if you use FS413 (Johnson Creek Rd) you just need to cross the creek.