The Petrali - Carlheim tribute bike was built by Justin Walls of BTTW (Built the Traditional Way) for Bobby Green of Old Crows Speed Shop from a 1948 big twin 80” UL Flathead Engine converted to overhead valves by Gus Carlhheim in the late 1940’s for midget cars. The new bodywork hand fabricated by Justin is based on the original Joe Petrali land speed Knucklehead racer, although Justin improved both the design and the aerodynamics in his treatment. Photographed at the Born Free chopper show. Silverado, CA. USA. Sunday June 24, 2018. Photography ©2018 Michael Lichter. Photographed by Michael Lichter in Boulder, CO on 6/29/18. ©2018 Michael Lichter.