Reprinted from the February 1995 issue of the
Gas Engine Magazine

Hercules Engine News
Including Economy, Arco,
Jaeger & Thermoil

by Glenn Karch
Old State Road
Haubstadt, Indiana 47639 .

Once the cam gear and exhaust valve adjustments have been properly set, the third step, timing the ignition, can be made. Although there are several different ignition systems used on Hercules built engines, in this article the Webster system using the M, K and L magnetos will be discussed. The instructions given here are for engines to be run at or near rated speeds and that are intended to pull a load. It should be noted that if parts are badly worn or other repairs poorly made, the necessary adjustments may be hard to make and maintain. Further, these adjustment instructions can be used on other brands of engines once a timing reference point has been determined.

Some engine instruction manuals give the timing recommendations in terms of degree of spark advance ahead of inner dead center. Jumbo literature mentions eight degrees of advance for each 100 RPM; i.e. 40 degrees for 500 RPM and 28 degrees for 350 RPM. Racine-Sattley literature lists 35 degrees for the 1 HP graduated down to 15 degrees for the 15 HP. These recommended advances appear to be greater than those obtained when properly setting the advance for Hercules built engines. The degree of timing advance depends on a number of factors, including RPM, stroke length, flywheel weight and flywheel diameter.

In the next article the discussion will cover timing and other adjustments for slow running show engines.

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