Make sure to keep your eyes open for the brown post that marks the top of Lower Holy Jim. Heading east and up the Main Divide Rd you'll see the post on your left in the shade of a large tree. The trail that drops away from the fire road is at first steep, and filled with large boulders, so unless you're advanced or dumb, just walk the bike down to the bottom of the leaf covered hollow where a much more manageable singletrack resumes.
At first, under the tree canopy, the trail climbs for a few hundred yards, then starts a descent that won't stop for a few thousand feet. The amounts and variety of terrain that Lower Holy Jim traverses is really impressive. There are stretches of north facing trails through thick seas of bush and tree six feet high, obscuring the tight switchback around the next blind turn. The south facing slopes, with their dry desert-like scrub, are fast but can have loose, sandy footing. And the switchbacks never seem to end.
Once you reach the creek bed, the terrain turns almost rain forest. There are a handful of creek-crossings to navigate, along with the rocks and boulders that accompany this very picturesque canyon. Watch for hikers now, this is the lower section more readily accessible to the slower half of us.
As you near the end of the trail, you'll pass a ranger station and a trailhead and, eventually, a wide intersection of dirt roads. This is Trabuco Canyon Rd
and is the end of Holy Jim Canyon.