Hercules Gas Engine Restoration

Peter Rooke tackles a circa-1923 Hercules Economy Model F gas engine.

| August/September 2015

This is part 1 of Peter Rooke's series on restoring a circa-1923 Hercules Economy Model F engine. Continue reading in part 2.

Hercules background

Another tired old engine has joined my collection, a circa-1923 Hercules Economy Model F, serial number 290,884. The Economy engines were first made in Sparta, Michigan, by the Holm Machine and Manufacturing Co. for Sears, Roebuck & Co. By 1912 Holm could not keep up with demand. The Hercules Gas Engine Co. was formed that year, having purchased Holm and started work building a new factory in Evansville, Indiana. The first Hercules produced engines were sold in January 1914 and were known as the Model D. The Economy engine produced for Sears differed slightly in design to the Hercules, having a more rounded lip to the water hopper, no crank guard and being painted red rather than Hercules green.

The Model E was popular, with some 220,000 engines sold. It was followed by the Model F, which was produced from 1921 to 1923. An estimated 25,000 Model Fs were produced that incorporated design modifications including the supply of Webster 1A and 2C magnetos. These magnetos did not prove popular, and many engines were later converted to use either Wico EK high-tension magnetos or fitted with the older Webster oscillating magneto. Looking at what was left of the trip finger clamp on the pushrod on my engine, it would appear it had been converted to run using a Wico EK.


From looking at photographs I received before purchasing the engine, I knew numerous parts were missing, including the muffler, igniter, magneto, rocker arm, fuel tank and fuel filler spout. There was a large toothed sprocket fitted to the crankshaft, and I was advised that this probably was used in a cement mixer. Hercules sold engines to Jaeger to use on cement mixers, so before doing anything I carefully examined the side of the engine casting to see if I could find any holes where another nameplate might have been fitted. There were none.

The entire engine was covered in rust and there was some bad pitting to the flywheels. Grease around the crankshaft bearings had protected the paint in that area and there were specks of red paint still showing. That suggested this was an Economy engine.

After using the hoist to get the engine on the workbench, the first task was to remove the sprocket and examine the crack at one end of the flywheel hub. The sprocket proved to be stubbornly in place. After applying plenty of lubrication, a hydraulic puller was used to remove it.