Dick Troutman and Tom Barnes (builder of Lance Reventlow' Scarabs, Pete Brock's Samauri, and the first Chaparrals for Jim Hall) also built some motorbikes. Here are two shots of their 450 Honda engined desert bike. Photos are from the 06/68 Cycle World.
The frame used 4130 steel and all tubes but steering head and swingarm 1.25" x .049" wall, and the swing arm was 1.375" x .095" wall. Engine and shock absorber mounting plates were of .125" sheet. Wet weight - 328 pounds. Engine - 4 speed Honda 450 with 40mm DCOE Weber carb.