The Vega .61 4-cycle, side-valve model airplane engine was built by John Harbone of Birmingham, England, 1988-1995. Side-valve (flathead) engines have the valves located in the crankcase alongside the cylinder driven by the camshaft within the crankcase. This arrangement requires no tappet adjustment and offers an engine much more compact in size.
All of the engines were machined in small quantities from aluminum and steel bar stock and were designed to burn methanol with castor oil mixed in for lubrication. Single cylinder variations included a .25, .30, and .91, and two sizes of opposed twins included a .50 and 1.8. Cutaway work by Paul Knapp.