Specifications

17
ENGINE/ALTERNATOR REPLACEMENT INFORMATION
With the exception of the AC Only alternator, all of the alternator systems referred to in this book have a
battery as part of the electrical system.
There are specialized applications that use an alternator without a battery. An example would be certain
generators or welders that use alternator output to excite an electrical field. For the equipment to function, the
alternator output must be very evenly matched to the equipment requirements. When replacing an engine in
these applications, the alternator must be the same as the original.
REPLACING BRIGGS & STRATTON® ENGINES
When replacing an older Briggs & Stratton engine on a piece of equipment with a newer Briggs & Stratton
engine, sometimes the newer engine has an alternator system different from the alternator system on the
original engine. This means that the output connector on the replacement engine is not compatible with the
original wiring harness on the piece of equipment. For example, the original engine may have been equipped
with a Dual Circuit system and the replacement engine is equipped with a regulated system. We can integrate
the two systems by making an adapter harness from readily available parts.
Generally an unregulated DC system (DC Only, Dual Circuit) should not be used to replace a regulated
system because alternator output may not be sufficient for equipment requirements. However, because the
equipment requirements are usually much less on an unregulated DC system, a regulated system may be
used as a replacement. The regulator/rectifier prevents the battery from being over charged.
NOTE: The AC Only, DC Only, Dual Circuit, Tri-Circuit as well as the 5 and 10 amp regulated systems use
flywheels with small alternator magnets. The 9 and 16 amp regulated systems use flywheels with the
large alternator magnets. See figure below for magnet sizes.
ALTERNATOR
MAGNETS
*Small Magnet 7/8" x 11/16"
(22mm x 18mm)
*Large Magnet 1-1/16" x 15/16"
(27mm x 24mm)
*V Twin Alternator Magnet Size: Small 7/8" x 21/32" (22 mm x 17 mm)
Large 7/8" x 29/32" (22 mm x 23 mm)