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Subaru introduces the EX40 overhead cam engine, now the largest model
in its line of high performance air-cooled, 4-cycle EX Series engines.
Delivering a maximum output of 14-horsepower, the EX40 effectively
opens up the EX Series to a new level of applications, including
general construction equipment, power generators, compressors and small
Utilizing chain-driven overhead cam (OHC) technology, the new engine
offers more power, easier starting and quieter operation than
competitive engines in its class. OHC technology allows the EX40’s
intake and exhaust valves to be positioned to offer lower resistance
for the air/fuel mixture flow, thus optimizing engine performance.
Designed with a highly efficient pent-roof combustion chamber, the EX40
is able to utilize a high compression ratio to produce higher power and
The EX40 meets both CARB and EPA Tier 3 emission standards, thanks in
part to an OHC valve narrow-angle layout that enables the combustion
chamber to function without a special catalyst. Furthermore, enhanced
cooling balance contributes to higher combustion efficiency, thereby
lowering fuel consumption.
Easier starts are another advantage of the EX40. An automatic
decompression timing system reduces the required recoil pulling force
by 30- to 40-percent when compared with overhead valve (OHV) engine
designs. In conjunction with the optimized combustion chamber design,
starts are fast and easy with no perceptible kickback.
The EX40 is engineered with an inclined cylinder, lighter-weight parts,
and improved rotation balance to make it easier to mount onto
machinery. Additionally, the new engine’s mount and center height are
the same as current EX models to ensure compatibility.
With fewer moving parts, OHC engines produce less mechanical noise than
competitive technologies. The EX40 takes it a step further by utilizing
optimized-capacity rigid mufflers and a new resinous air cleaner.
Together these features make the EX engines a full 2 dBA quieter in
exhaust tone than other same-class engines.
Excessive heat is the primary cause of engine failure. To combat this
problem, the EX Series features Subaru’s patent-pending technology to
provide outstanding cooling performance. To utilize every possible
cooling area, special heat dissipation fins have been built into the
mounting base, cylinder and both the inner and outer crankcase
surfaces. Additionally, the OHC technology allows for 360-degree
airflow around both the exhaust and intake valve stem areas.
Engine durability is further enhanced by a patent-pending oil delivery
system. A unique oil scraper attached to the connecting rod supplies
oil to the cam chain. The cam chain then carries the oil to the
overhead cam and valve train. A special rocker cover design and
breather system keep the camshaft and rocker arm bathed in oil, yet
prevent spouting — whether the engine is level or inclined.
Since arriving on the market in 2001, the Subaru EX Series has sold
approximately 1.7 million units worldwide. The four original models —
ranging in piston displacement from 126 cc to 265 cc — have been rated
highly by users for achieving both outstanding low-emission
environmental performance and user-friendliness, such as low noise and
easy start-up operation, while keeping durability and reliability
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