Reprinted from the
April 1999 issue of the
Gas Engine Magazine

Hercules Engine News
Including Economy, Arco,
Jaeger & Thermoil

by Glenn Karch
Old State Road
Haubstadt, Indiana 47639

The question comes up frequently in regard as to how to properly time a Hercules built engine. To set timing properly, three steps must be taken, and in proper order. The first of these steps is to set the timing properly. Shown below is the explanation taken directly from the instruction book.

The second step is to set the exhaust valve timing. The exhaust valve should start to open when the crankshaft is about 45 degrees before bottom dead center on the power stroke It should remain open until the crankshaft is 3 to 5 degrees past top dead center at the beginning of the intake stroke. Turning the screw in or out that is on the end of the exhaust rocker arm makes this adjustment.

The final step is then the ignition timing. On all except the igniter, battery and coil-equipped engines, there is a lever with a retard and run position. For an engine expected to run at rated RPM and to pull a load, the spark should occur when the "spark" mark on the flywheel is even with the top of the side rod and the lever set in the run position. On the Webster system, the run position is when the lever is straight up. On the Wico system, the run position is when the lever on the trip finger mechanism is in the down position. With these adjustments, ignition should take place between 20 and 25 degrees before top dead center depending on the engine size. When the lever is set in the start position, the ignition should take place at about top dead center. For show engines running much slower, reset ignition timing in the run position to about 4 degrees advance for each 100 RPM. The run-start position for the Webster system is shown m the illustration below. In case you didnít notice it, I now have an e-mail address as shown at the top of this page.

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