We started at its southernmost end at the Scenic Loop's juncture with Utah State Highway 132 near Nephi, Utah.
The Scenic Loop road is very twisty in mostly excellent condition for ~75% of its length. For cruiser motorcycles, it will be a very easy and enjoyable ride.
For sport bike riders, it might be enjoyable if you're okay with riding mostly in first and second gear.
The southern 75% of the trip had very little traffic and very few people. We had the mountainous area mostly to ourselves. The views were magnificent.
If you're into primitive camping, we recommend this area. There are plenty of roads that lead somewhere away from the main road and are not maintained campgrounds.

The Northern part of the ride begins to deteriorate at the Payson Lakes area. The traffic significantly increases from this point to Payson with some people rudely doing about 8 mph. ;^) The pavement quality steadily deteriorates all the way into Payson where some small sections have no pavement. There was construction going on to repair this area on the day we were there. Check the Utah Commuter Link for up-to-date information before you go.
The Payson Lakes area is worth commenting on. There are some nice campground areas there and three beautiful, small mountain lakes surrounded by green, lush trees. They look like a welcome respite from hot weather on a summer day with quite a few people paddling small rafts on them.
There are plenty of good places to hike along the way. The Monument trail head, above 9000 feet and near the Scenic Loop's peak at 9345 feet, looks to be the best place to hike/climb Mt. Nebo with almost 3,000 vertical feet. Mount Nebo is crowned by three peaks, with the northern peak reaching 11,928 feet. Original surveys placed the southern peak as the highest at 11,877 feet. Unfortunately, when the mountain was resurveyed in the 1970s and the northern peak was found to be the highest, two substantial trails already led to the south summit. Parts of the mountain are covered in snow from mid-October until July. It is a popular, although strenuous, destination for hikers.

The southern entrance to the Mt. Nebo Scenic Loop is approximately 90 miles from Salt Lake City, about 1 hour elapsed time.
Take Interstate I-15 south to State Highway 132, the second of three Nephi exits, turn east, and look for the Mt. Nebo Scenic Loop sign in about 5 miles.
The day we rode was a very hot day with a haze of smoke in the air from forest fires, as you can see from this photo looking down into the valley and town below with Utah Lake in the background.
It felt wonderful to go up high and enjoy cool breezes and clean air. The thing that impressed us the most, other than the views and the cobalt blue sky, was the immense silence. All we could hear was the gentle wind rustling through the trees. Definitely a motorcycle road trip to take on a warm summer weekend.