The cutaway cross-sectional view shows some of the major components of the EX30 engine.
Dual ball bearing crankshaft support offers maximum stability under demanding loads.
The crankshaft is made of spheroidal graphite cast iron, and the crank
pin is high-frequency induction hardened. Both the crank sprocket used to
drive the chain, and the gear used to drive the governor gear,
are pressed on the output end of the shaft.
Cast-iron cylinder liners enhance reliability and extend engine
life. The cast iron cylinder liner has much better wear characteristics
the softer aluminum that surrounds it, making engine life much longer
than if the piston is in contact with the aluminum cylinder wall.
Case-hardened steel timing chain allows for precision timing and maximum durability.
Overhead Cam (OHC) technology and the Pent-Roof combustion chamber
allow the Subaru EX engines to use a higher compression ratio of 9:1.
The higher compression ratio increases the power produced for a given
size engine. It also improves efficiency and overall performance.
The illustration shows the straight intake port on the right side of
the picture. The lower resistance to the flow of the air/fuel mixture
improves the power, efficiency and lowers emissions. Overhead Cam (OHC)
technology allows the intake and exhaust valves to be positioned for
Subaru EX engines use automotive quality collet valve retainers for longer life.
Hardened steel rocker arms with precision tappet adjusters are used for greater durability and reduce service requirements.
Cooling fins are cast into both the inside and the outside of the crankcase to utilize every possible cooling area.
The unique Subaru cooling system extends to the underside of the
mounting base. Air is forced over special cooling fins at the bottom of
the engine for maximum cooling.
Head cooling is critically important to long engine life. The Overhead
Cam design allows for 360-degree air flow around both the exhaust and
intake valve stem areas.
The EX lubrication system begins with a patent-pending oil scoop to project the oil to the chain.
Air is forced over the large slanted cooling fins on the cylinder for
improved cooling performance. This design is patent-pending.
The connecting rod is a specially heat-treated aluminum alloy
die-casting. Its large and small ends function as bearings. A splasher
built into the connecting rod lubricates by splashing engine oil. The
piston is an aluminum alloy casting with grooves for mounting
compression and oil rings.
A patent-pending rocker cover design constantly
supplies an optimum amount of oil to the cam
shaft and rocker arm even if the engine is
A patent-pending breather system with a pre-separation
passage prevents oil from spouting even if the engine is inclined.
This cross-sectional view shows many internal components of the EX30 engine.
The ignition system is a transistor controlled magneto with the
ignition timing set at 23 degrees before top dead center. The magneto
consists of a flywheel and ignition coil. To ensure the easy
startability of the engine, the step advancing ignition timing system
is incorporated in the ignition coil. This system enables the engine to
have basically two different ignition timings according to the engine
Optimized-capacity rigid muffler and 33 percent fewer moving valve
train parts than OHV designs, reduce mechanical noise levels a full 2
decibels below competitive models.
Even though the EX series of engines bring the latest technology,
performance, and durability to the industrial air-cooled engine market,
there are no special tools required to work on them. All the
shop tools that most small engine mechanics currently own will also
work on these engines for service or complete teardown. Subaru engineers achieved their commitment to 'keep it simple', while utilizing the latest technology.