Troubleshooting; Operation - Shindaiwa 300 Service Manual

Section
2 Troubleshooting
The 2-Stroke Cycle Engine
Theory
01
Operation
Figures 2. 1 and 2 2
A two-stroke cycle or
"two-cycle " engine
produces one power
stroke for every
revolution of its
crankshaft. Intake
and compression
occur during the
piston's "up " stroke;
power and exhaust
occur during the
"down" stroke.
Six distinct pro­
cesses occur during
every revolution of
the crankshaft, and a
1055
or weakness of
even one of these
processes wi/l affect
the other five.
Piston Ported Induction
1. Intake
A.S Ihe piston moves up towar the cyl lnder
head a low pressure (vacuum) is created In
the crankcase . As the movlng pistan uncovers
he
i
ltake por t, atmosphenc pressure pushes
a fresh charge 01 fuel-air nixture in ta the
crankcase .
The mi xture ac comp1 ishes two functions
befare il is moved to he combu sti on chamber:
• Oi1suspended in lhe mixture coats all
Internal engine parts includlng cylmder
wall s crankshaft. and bearings.
• The atomlzed fuel mi xture absorbs hea! as
il enters !he crankcase . lowerlng lhe
engine's opera ti ng temperalu re .
2. Compression
As the piston continues lo move upward and
cover lhe cy linder ports, the combust lon
chamber is sealed and compression begins
The ajr-fuel mixture introduced during Ihe
p revio us
revolution's lfans/er cycle is now
tra pped and becomes compressed between
Ihe piston and cyli nder head
3.lgnition
As the piston a proac hes the lap t Ihe
cylinder, lhe spark plug fi res and gnl es lhe
fuel -air mi xture . To compensale lar increases
in eng ine rpm.
spar k
liming is advanced
electron ical1 y.
Spark plug
Intake
port
open
Vacuum
F/9ure Z
1
Crankcase vac m;8 created dunng Ihe
compression stroke When Ihe spark plllg (¡res ¡he
compressed mixture al>nve l/le Dlston ¡gil/les and
begms
ro
e ano
Shlndaiwa Inc 1995
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