This view shows the air cleaner removed and the throttle body's main components.
This cutaway view of the single piece throttle body gives a description of some of the components and connections.
This view shows the Delphi Injector in the cavity of the throttle body. This injector is easily serviced.
In this picture, the flywheel, air cleaner, recoil, throttle body and gas
tank are removed to show the main components of fuel injection, power coil and
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.
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.
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.
Subaru EX engines use automotive quality collet valve retainers for longer life.
The camshaft and the sprocket are made of special sintered alloy and constructed as a single piece. The camshaft is provided with intake
and exhaust cam in one cam lobe. The decompression release lever is
mounted on the sprocket end side.
Dual ball bearing crankshaft support offers maximum stability under demanding loads.
Hardened steel rocker arms with precision tappet adjusters are used for greater durability and reduce service requirements.
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
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 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
Special machining on cylinder head allows the oil seal to be placed
around the valve guide. This seal reduces oil consumption and is
replaceable for service.
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.
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.
The EX lubrication system begins with patent-pending oil scoop to project the oil to the chain.
A patent-pending breather system with a pre-separation
passage prevents oil from spouting even if the engine is inclined.
Air is forced over the large slanted cooling fins on the cylinder for
improved cooling performance. This design is patent-pending.
A patent-pending valve cover design constantly
supplies an optimum amount of oil to the cam
shaft and rocker arm even if the engine is
Cooling fins are cast into both the inside and the outside of the crankcase to utilize every possible cooling area.
The crankshaft is made of spheroidal graphite cast iron, and the crank
pin is high-frequency induction hardened. The crank sprocket used to
drive the chain, as well as the gear used to drive the governor gear,
are pressed on the output end of the shaft.
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 this engine. Most
shop tools that small engine mechanics currently own, will also
work on this engine for service or complete tear down. The commitment by
the Subaru engineers to 'keep it simple', but use the latest technology was achieved.