Shindaiwa 357 Service Manual download pdf (Page 32)

Q Shindaiwa Inc. 1995

32

Section 3 Carburetors

HDA and WT

Dissassembly

(continued)

CRB-21

Diaphragms (continued)

■ Place the individual diaphragms over a

lighted flashlight lens or microfiche screen.

Replace any diaphragm showing evidence of

pinhole leaks or other damage.

Metering Valve

■ Use a magnifying glass to inspect the inlet

valve tip for signs of measureable wear,

and replace if noted (Figure 3.22)

■ Inspect the metering lever spring for

deformation or other damage, and replace

if noted.

■ Inspect the metering lever for signs of wear

at the forks, hinge-pin, or tip. Replace any

lever showing signs of measureable wear

(Figure 3.23).

IMPORTANT!

A worn metering lever cannot be properly

adjusted, and could cause the saw to run in

either a fuel “rich” or fuel “starved” condi-

tion! If valve serviceability remains doubtful,

reinstall the metering assembly and then

pressure-test the carburetor for pop-off and

reseat pressures as described on page 34.

Main Nozzle Check Valve

Mechanical check valves can be quickly

tested by gently blowing through a small hose

inserted in the cup plug bore.

■ If the valve is functioning properly, it will

permit airflow towards the venturi only.

■ If the valve must be replaced, remove the

high speed adjustment screw and press or

drive the deffective valve out through the

venturi bore.

Installation of a new valve (available from

Walbro) is similar, except that the new valve is

installed from the metering chamber.

IMPORTANT!

Capillary screen valves function by main-

taining a thin film of fuel over the screen

mesh, allowing fuel to pass through the

screen but blocking air from entering the

carburetor through the main nozzle.

Good Replace

Figure 3.22 Check Inlet Valve Tip for Wear

CARBURETORS

CRB-27

Inlet Valve

Seat

Pin

Forks

Spring

Lever

Figure 3.23 Metering Valve Installation

Tip

Valve

Tip

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