Shindaiwa 357 Service Manual download pdf (Page 8)

Q Shindaiwa Inc. 1995

Section 2 Troubleshooting The 2-Stroke Cycle Engine

Reed Valve Induction

as used on Model 357

Figures 2.3 and 2.4

1. Intake

As the piston moves up toward the cylinder

head, low pressure (vacuum) created in the

crankcase allows atmospheric pressure to

open the reed valve and push a fresh charge

of fuel-air mixture into the crankcase.

The fuel-air mixture accomplishes two

functions before it is moved to the combustion

chamber:

■ Oil suspended in the mixture coats all

internal engine parts including cylinder

walls, crankshaft, and bearings.

■ The atomized fuel mixture absorbs heat

from the crankcase, lowering the engine’s

operating temperature.

2. Compression

As the piston continues to move upward and

cover the cylinder ports, the combustion

chamber is sealed and compression begins.

The air-fuel mixture introduced during the

revolution’s transfer cycle is now

trapped and becomes compressed between

the piston and cylinder head.

3. Ignition

As the piston approaches the cylinder head,

the spark plug fires and ignites the fuel-air

mixture. To compensate for increases in

engine rpm, spark timing is advanced

electronically.

Theory of

Operation

TROUBLESHOOTING

Figure 2.3 Reed Valve Induction System (reed valve open)

CRB-75

Spark Plug

Low Pressure

Reed Valve Open

Combustion and

Compression

Exhaust and Transfer

Ports (closed)

1 2 3 4 5 6 7 8 9 10 11 12 13 ... 137 138

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Shindaiwa 357 Service Manual Page 8

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