These engines were built by Stover Mfg. & Engine Co. of Freeport, Illinois and sold under the Cooper Engineering Co. name. Cooper were the Australian agents.
In August 2002 Ron Sullivan swapped an engine for two Stover YB engines. One fairly complete the other consisting of the head and valves, cylinder, piston and rod, crankshaft and crankcase and one flywheel. Pretty much everything else was missing. I did a deal with Ron and ended up with the project YB. I was lucky to acquire the missing flywheel and the base off Edd Payne but I continue hunting for more parts. I have been gradually taking parts of Ron's engine and getting new parts cast for my engine. I now have almost everything cast for the engine.
Below are the two YBs ron picked up. The one missing all the parts is mine the more complete one is Rons.
The engine number on my YB is YB95063 and was shipped from Stover to Coldwell Shipping Co.,San Fransico, California on August 13th 1917.