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Stihl MS 311 User Manual - Page 14

Carburetor

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3.6 Carburetor Condition Carburetor floods; engine stalls Cause Remedy Inlet needle not sealing - foreign matter in valve seat or cone Remove and clean the inlet needle, clean the carburetor Inlet needle worn Replace the inlet needle Inlet control lever sticking on spindle Check the inlet control lever and replace if necessary. Helical spring not located on nipple Remove the inlet control lever and of inlet control lever refit it correctly Perforated disc on diaphragm is deformed and presses constantly against the inlet control lever Fit a new metering diaphragm Metered diaphragm deformed Fit a new metering diaphragm Poor acceleration Setting of low speed screw too lean Check basic carburetor setting, correct if necessary Setting of high speed screw too lean Check basic carburetor setting, correct if necessary Inlet needle sticking to valve seat Remove inlet needle, clean and refit Diaphragm gasket leaking Fit new diaphragm gasket Metering diaphragm damaged or shrunk Fit a new metering diaphragm Tank vent faulty Replace tank vent Leak on fuel hose from tank to carburetor Seal connections or install new fuel hose MS 311, MS 391 13

Section	Page
Contents	2
1. Introduction and Safety Precautions	4
1.1 Introduction	4
1.2 Safety Precautions	5
2. Specifications	6
2.1 Engine	6
2.2 Fuel System	6
2.3 Ignition System	6
2.4 Chain Lubrication	6
2.5 Tightening Torques	7
3. Troubleshooting	9
3.1 Clutch	9
3.2 Chain Drive, Chain Brake, Chain Tensioner	10
3.3 Chain Lubrication	11
3.4 Rewind Starter	12
3.5 Ignition System	13
3.6 Carburetor	14
3.7 Engine	17
4. Clutch	18
4.1 Clutch Drum	20
5. Chain Brake	21
5.1 Checking Operation	21
5.2 Brake Band	21
5.3 Brake Lever	23
5.4 Cam Lever	25
5.5 Pins	26
5.6 Chain Tensioner	26
5.7 Bar Mounting Studs	27
6. Engine	28
6.1 Muffler	28
6.2 Leakage Test	29
6.2.1 Preparations	29
6.2.2 Vacuum Test	30
6.2.3 Pressure Test	30
6.3 Oil Seals	31
6.4 Shroud	32
6.5 Cylinder / Crankshaft	33
6.6 Bearings / Crankshaft	36
6.7 Piston	37
6.8 Piston Rings	39
6.9 Decompression Valve	39
7. Ignition System	40
7.1 Ignition Timing	40
7.2 Preseparator	40
7.3 Ignition Module	40
7.4 Testing the Ignition Module	42
7.5 Spark Plug Boot / Ignition Lead	43
7.6 Flywheel	44
7.7 Short Circuit Wire	45
7.7.1 Testing	45
7.7.2 Removing and Installing	45
7.7.3 Ground Wire	47
7.7.4 Contact Spring	47
7.8 Ignition System Troubleshooting	49
8. Rewind Starter	52
8.1 General	52
8.2 Fan housing	52
8.2.1 Segment	52
8.3 Pawls	52
8.4 Rope Rotor	53
8.5 Starter Rope / Grip	54
8.6 Tensioning the Rewind Spring	55
8.7 Replacing the Rewind Spring	56
9. Servicing the AV System	58
9.1 Buffer on Oil Tank	58
9.2 AV Spring on Oil Tank	58
9.3 AV Spring on Fuel Tank	58
9.4 AV Spring on Front Handle	59
9.5 Stop Buffer at Clutch Side	60
9.6 Annular Buffer at Ignition Side	60
9.7 Handlebar	60
10. Control Levers	62
10.1 Master Control Lever	62
10.2 Throttle Trigger/Interlock Lever	62
10.2.1 Choke Rod	64
10.2.2 Throttle Rod	65
11. Chain Lubrication	66
11.1 Pickup Body	66
11.2 Oil Suction Hose	66
11.3 Oil Pump	67
11.4 Valve	68
12. Fuel System	69
12.1 Air Filter	69
12.2 Baffle	69
12.3 Filter Base	69
12.4 Air Guide Shroud	70
12.5 Carburetor	72
12.5.1 Leakage Test	72
12.6 Servicing the Carburetor	73
12.6.1 Metering Diaphragm	73
12.6.2 Inlet Needle	74
12.6.3 Pump Diaphragm	75
12.6.4 Air Valve	77
12.6.5 Levers on Throttle Shaft	77
12.6.6 Adjusting Screws	78
12.7 Carburetor Adjustment	80
12.7.1 Basic Setting	80
12.7.2 Standard Setting	81
12.8 Carburetor Carrier	82
12.9 Intake Manifold	83
12.10 Tank Vent	84
12.10.1 Testing	84
12.10.2 Removing and Installing	85
12.11 Fuel Intake	85
12.11.1 Pickup Body	85
12.11.2 Fuel Hose	86
12.11.3 Fuel Suction Hose	87
12.11.4 Tank Housing	88
13. Special Servicing Tools	89