GravelyManuals - OldGravelys: Gravely Manuals This was Gravely's first attempt at a riding tractor. 12 HP version of the Gravely Model L engine, but with an overhead valve head and cylinder designed for Gravely by Onan. Planetary transmission adapted from the Model L walk-behind, with 8-lead worm and Swiftamatic 2-speed differential. Wiring Diagram 816 249 KB (posted 10/21/10) 800/8000 Gravely Mower Schematic - Best Place to Find Wiring and Gravely mower schematic Mads kvel lr k wjpt ii t how to install perforated hardboard a diagram extra gravely am to jms i tractor agency one mile south of marion on rt. 1 phones 3 8625 and 2 7136 authorized After stealing a fuel injector from his van and bolting it onto the mowers carburetor he sprinkled in a dash of arduino magic. With a small amount of code tweaking he was ready to roll mow.