Cayuse Pass sits at about 1,430 metres on the eastern flank of Mount Rainier, and its main job is to be a junction. State Route 123 comes up from the south along the Ohanapecosh side, State Route 410 arrives from the north out of the Greenwater valley, and just beyond the crest the road keeps climbing east toward the higher Chinook Pass. You arrive through old-growth forest, Douglas fir and western hemlock so tall that the road feels like a tunnel, and then the trees thin and you are standing in subalpine meadow with the mountain somewhere above you, usually in cloud.
The riding here is the sort that does not need to be fast. The corners are long and open, the asphalt in the national park is generally kept in decent shape, and the speed limits are low and enforced by rangers who have seen every kind of motorcycle. Traffic is the real variable. On a July weekend the lay-bys fill with cars and the pace drops to that of the slowest camper van, so go early in the morning or on a weekday, or come in September when the huckleberry bushes turn red and the crowds have gone back to school.
Timing matters more than usual, because this is a seasonal road. Snow in this part of the Cascades is measured in metres, and both 123 and 410 over the passes are closed through the winter, usually reopening late spring and sometimes not until the plough crews have fought through a heavy year. Check the state road reports before you plan a loop around it. The weather can turn in an hour: you can leave the lowlands in sun and meet fog and four degrees at the pass.
Rainier itself is a volcano, around 4,400 metres high, and the most heavily glaciated peak in the lower forty-eight. You will mostly see it as a vast white shape appearing and vanishing between the clouds, and that is part of the pleasure. Do not count on the pass for anything but views: arrive with a full tank, filled in Enumclaw to the north or Packwood to the south. Bring a layer more than you think you need, and watch the margins of the road at dusk, because deer and the occasional black bear use the same clearings you do.