Just northeast of Des Moines, start on NW Horseshoe Rd, then take the road that travels along the dam side of the lake (no name assigned to the road) and head west until you come to a fork in the road and will want to take the short left and then take a right on to NW 78th Ave. Take this to NW Beaver Rd where you want to take a right and start to head northwest along the west side of the lake. Then when you get to route 415 (NW Saylorville Rd) take a right and head east and cross over the lake on the bridge. 415 will T into 3rd Street. Here you want to take a right on to 3rd street (the road continues with you as route 415) and start heading south along the east side of the lake. This will basically take you back to where you started when you hit NW 84th Ave and take a right and see your original starting point (NW Horseshoe Rd).
The Saylorville Loop is a popular cruise for may motorcyclists. The loop takes you across the spillway and over the Mile Long Bridge. Some nice slow, curvy roads take you across the Lake and through the woods. Make sure to stop at the pull off point on the spillway to get a photo of your bike with the lake in the background.
Sweeping, slow curves. Nice newer pavement. Keep an eye out for wildlife and sand/dirt in some of the intersections.
Feel free to pull off the loop in either Johnston, Polk City, or Ankeny for just about any food you could want.
Motorcycle Road Additional info
Watch for mobile speed unit on the spill way bridge. The speed limit here slows to 25 mph and its very tempting to hit those corners going faster. RESIST!