STIHL 017-018 FUEL SYSTEM Routine Repair Guide

STIHL 017-018 FUEL SYSTEM Routine Maintenance Guide

Dirty and clogged air filters reduce engine power, increase fuel consumption and make starting more difficult.

Air Filter

The air filter should always be cleaned when engine power begins to drop off.

– Remove the shroud

– Clean away any loose dirt from around the filter

• Remove the filter element

– Wash the filter element in a fresh, non-flammable cleaning solution (e.g. warm soapy water) and, if possible, blow out with compressed air. Soften encrusted dirt by soaking the parts in cleaning solution.

Note: If filter is damaged, install new part immediately

Reassemble in the reverse sequence.

Filter Housing

– Remove the shroud
• Unscrew the mounting nuts.

• Pull away the filter housing.
– Inspect the filter element

Install in the reverse sequence.
Note: Tighten mounting nuts to 3.5 Nm (2.6 lbf.ft).

Carburetor Leakage Testing

The carburetor can be tested for leaks with the carburetor and crankcase tester.

– Remove the shroud

Pull fuel hose off carburetor elbow connector.

Removing and Installing

• Use fuel line (1) with nipple (2) as adapter to make connection between tester and carburetor elbow connector.
• Push the nipple into the tester’s pressure hose (4).
• Close the vent screw (5) on the rubber bulb (6) and pump air into the carburetor until the pressure gauge shows a reading of approx. 0.4 bar (5.8 psi).

If this pressure remains constant, the carburetor is airtight. However, if it drops, there are two possible causes:

1. The inlet needle is not sealing (foreign matter in valve seat or sealing cone of inlet needle is damaged or inlet control lever
sticking).
2. The metering diaphragm is damaged.

In either case the carburetor must be removed and serviced

– After completing test, open the vent screw and pull the fuel line off the elbow connector.

– Push the fuel hose onto the carburetor elbow connector.

– Fit the shroud

– Remove the switch shaft
• Pull the fuel hose off carburetor elbow connector.

Disconnect the throttle rod from the throttle shaft.

• Pull the carburetor off the mounting studs.
Install in the reverse sequence.

Note: Before installing carburetor, check that sleeve is in position in manifold.

Carburetor Adjustment

The carburetor is equipped with a fixed jet in place of the high speed adjusting screw (H screw).
Maximum engine speed is permanently set and cannot be adjusted. Only the engine idle speed can be adjusted within fine limits.
The carburetor guarantees an optimum fuel-air mixture in all operating conditions.

Standard setting

If the carburetor has to be adjusted from scratch, first carry out the standard setting.

Carefully screw down the low speed adjusting screw (L) until it is hard against its seat. Then open it one full turn counterclockwise.

– Check chain tension.
– Check air filter and clean if necessary.
– Start the saw – warm up the engine.
– Adjust idle speed correctly (chain must not rotate).

Adjusting idle speed

It is usually necessary to change the setting of the idle speed screw (LA) after every correction to the low speed adjusting screw (L).

Note: Turn screws very slowly and carefully – even slight adjustments produce a noticeable change in engine running behavior.

Engine stops while idling – Check standard setting.

Turn idle speed stop screw (LA) clockwise until the chain begins to run – then turn it back one quarter turn.

Chain runs while engine is idling – Check standard setting.

Turn the idle speed stop screw (LA) counterclockwise until the chain stops running – and then turn it about another half turn in the same direction.

Erratic idling behavior, poor acceleration – even though low speed adjusting screw is one turn open

Idle setting too lean. Turn the low speed adjusting screw (L) counterclockwise until the engine runs and accelerates smoothly.

The diaphragm pump draws fuel out of the tank and into the carburetor via the fuel hose. Any impurities mixed with the fuel are retained by the pickup body (filter). The fine pores of the filter eventually become clogged with minute particles of dirt. This restricts the passage of fuel and results in fuel starvation.

Important: In the event of trouble with the fuel supply system, always check the fuel tank and the pickup body first. Clean the fuel tank if necessary.

• Unscrew the filler cap and drain the tank.
– Pour a small amount of cleangasoline into the tank.
– Close the tank and shake the saw vigorously.
– Open the tank again and drain it.
Note: Dispose of old fuel at approved disposal site.

Pickup body
• Use the assembly hook (1) to pull the pickup body out of the fuel tank.
Note: Do not stretch the fuel hose while removing it.

• Pull the pickup body off the fuel hose.
– Fit a new pickup body.
Reassemble in the reverse sequence.

Correct operation of the carburetor is only possible if atmospheric pressure and internal fuel tank pressure are equal at all times. This is ensured by the tank vent.

Important: In the event of trouble with the carburetor or the fuel supply system, always check and clean the tank vent.

Note: Valve opening must be clean.

Equalization of pressure from the inside outwards takes place passed the sides of the valve.

– Remove the fan housing
– Drain the fuel tank.
• Pull fuel hose off carburetor elbow connector.

Pull the fuel tank out of the engine housing.

Remove the fuel hose (1) and valve (2).

Reassemble in the reverse sequence.

Note: When pushing the fuel tank into position, route the fuel hose between the straps on the engine housing (see illustration).

– Remove the fuel tank
• Use assembly hook (1) to pull the pickup body out of the tank.

• Pull the grommet off the fuel hose.
Reassemble in the reverse sequence.
Note: Coat the grommet with a little oil to simplify installation.

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