Engine Design & Theory - Shindaiwa T2510 Service Manual

Engine Design & Theory Of Operation
Air/fuel charge is pressure charged through the
C4 Engine:
second reed valve, into the boost chamber, en
Its Intake &
route to the intake valve. Along the way, the
Lubrication
fuel mix lubricates all valve train components.
Systems
The intake charge is pressurized because
during each cycle, the piston makes two down-
strokes, but the intake valve only opens once.
This constant pressure behind the intake valve
improves C4 performance compared to
ordinary four-strokes.
help reduce weight and complication, and to
eliminate the problems that oil reservoirs bring
to all-position engines, the C4 engine is
lubricated by a gas/oil fuel mixture, just like a
two-stroke. Gasoline containing low-smoke oil
mixed at a ratio of 50:1 bathes all critical
moving parts as it moves from crankcase, past
cam assembly to rocker box and valves. The
gas/oil mix is not an emissions problem
because of the lean ratio (98% gas, 2% oil) and
fact that intake and exhaust functions are
controlled by valves. The two-stroke's high
exhaust emissions occur due to exhaust
scavenging (unburned fuel) not the fuel/oil mix.
Unlike conventional four-strokes, the C4 engine
can run in any position, all day long. No
dipsticks, oil filling, breathers, or spilled oil to
worry about.
E. Service Considerations:
Because of its many two-stroke similarities,
many of the C4's service functions are the
same as Shindaiwa two-strokes. And,
wherever possible, Shindaiwa used the same
components and/or construction methods
found on Shindaiwa two-strokes. Thus, for
many service functions, such as carburetor
diagnostics and repair, shaft/gearcase
maintenance, recoil service, ignition service,
flywheel/clutch service, etc., technicians may
consult Shindaiwa's master trimmer /
brushcutter service manual.
The information in this service update will deal
primarily with functions related specifically to
the C4 engine.
Edition 2 • 09/2007
2. Two-Stroke Lubrication System: To
Special C4 logo and color
scheme set T2500 apart from
other Shindaiwa trimmers.
The T2500 engine requires
mixing oil with an ISO FC or
JASO EG-D rating. For best
possible results, Shindaiwa
recommends Shindaiwa One
oil at 50:1.
1
Section
4