Chain-driven Overhead Cam design offers superior power and performance with an automatic decompression system to reduce the required pulling force by 30 to 40 percent, and ensure starting on the first pull. EX engines start instantly – even at temperatures as cold as -10 degrees C – without any perceptible kickback.
Heavy-duty piston rings coupled with a cast-iron cylinder liner resist wear and ensure a long engine life.
Pent-roof combustion chamber enables optimum intake and exhaust valve placement for maximum engine performance and efficiency.
Case-hardened steel timing chain allows for precision timing and maximum durability.
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.
Hardened steel rocker arms with precision tappet adjusters are used for greater durability and reduce service requirements.
The EX lubrication system begins with a patent-pending oil scoop to project the oil to the chain.
Cooling fins are cast into both the inside and the outside of the crankcase to utilize every possible cooling area.
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.
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.
Subaru EX engines use automotive quality collet valve retainers for longer life.
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
A patent-pending breather system with a pre-separation
passage prevents oil from spouting even if the engine is inclined.
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. Most
shop tools that small engine mechanics currently own will also
work on these engines for service or complete tear down. Subaru engineers achieved their commitment to 'keep it simple', while utilizing the latest technology.