Stihl BR/SR 320, 340, 400, 420 & SR 430, 450 Blower/Mistblower Service Manual Collection – 2001 (P/N 0455 373 0123)

The manuals cover different model families. Use the matching publication for each machine: engine construction, ignition components, carburetor adjustments, and spraying equipment differ between families.

The illustrated parts lists referenced for replacement-part identification are separate publications; this collection contains the service manuals.

Searchable Text, Bookmarks and PDF Contents

Search and navigation: Searchable text and embedded PDF bookmarks span all three manuals. Ignition troubleshooting flowcharts and component callouts are readable, with zoom available for smaller details.

One printable, English-language PDF contains 250 pages. The total includes two front covers and two back covers within the publication page counts above.

Two-Stroke Engine, Ignition and Spraying-System Service

The following selected coverage highlights outline the main workshop content. Further topics include the early models’ ULV rotary nozzle and vacuum attachment.

• Engine repair: Step-by-step procedures for cylinder and piston removal, piston-ring replacement, crankshaft and bearing installation, crankcase sealing, and leakage testing.

• Fuel system: Carburetor pressure testing, diaphragm and inlet-needle service, mixture adjustment, tank-vent checks, and fuel-hose and pickup-body replacement.

• Ignition diagnosis: Spark testing, ignition-module replacement, flywheel inspection, short-circuit wire checks, and system-specific troubleshooting charts.

• Rewind starter: Rope rotor, starter rope, pawl, guide-bush, and rewind-spring replacement, with spring-tensioning procedures.

• AV system and controls: Vibration-buffer and spring replacement, throttle-cable adjustment, slide-control service, and variant-specific control-handle assembly.

• Spraying equipment: Container and metering-unit service, fanwheel removal, pressure-pump procedures, and separate SR 450 metering-cable and rotary-shutter work.

These manuals were written for STIHL servicing dealers and properly equipped repair shops, with specialist testing and assembly tools specified throughout.

Engine Construction and Leakage Diagnosis

The troubleshooting charts connect starting problems, erratic running, and overheating with possible faults across the engine and its supporting systems. Pressure and vacuum testing help distinguish crankcase leakage from carburetor-related symptoms; a seal can fail the vacuum test even when the pressure test reveals no leak.

The earlier manuals document two-part crankshafts, ball bearings, and needle cages. The crankshaft, connecting rod, and associated needle bearing form an inseparable replacement assembly. Crankcase assembly views also distinguish the early starter mounting with a spacer washer from the later modified mounting boss.

Oil-seal access differs: The earlier families allow seal replacement without complete crankcase disassembly. The SR 430/SR 450 procedure requires engine removal and engine-pan access.

The cylinder-installation instructions warn that rotating the cylinder after fitting it over the piston can break the piston rings. Oil-seal removal also carries a specific warning about damaging the crankshaft’s sealing surface with the puller.

Carburetor Service and Adjustment Differences

Carburetor assembly illustrations show the positions of the pump diaphragm, metering diaphragm, inlet needle, and control lever. The BR/SR 340/420 publication distinguishes HD 28, HD 29, and WT 520 carburetors, including their different limiter-cap arrangements.

The SR 430/SR 450 manual separates basic and standard carburetor settings and covers the manual fuel pump and fuel-hose connectors. Its pressure-pump attachment section describes removal and installation; internal pump disassembly is covered in the earlier publications.

Ignition Tests and Component Compatibility

Ignition timing is fixed, rather than a workshop calibration adjustment. The SR 430/SR 450 instructions explain that the ZAT 3 or ZAT 4 spark test does not verify ignition timing.

The ignition troubleshooting flowcharts work through the spark plug, module air gap, flywheel, stop switch, and ground and short-circuit wiring. Connection views identify the module terminals, while the BR/SR 340/420 instructions explain the compatibility change between the earlier crankcase and the replacement ignition module.

Starter, Mountings and Metering Equipment

Starter illustrations include the rope-guide-bush installation schematic and spring-clip positioning. The control sections distinguish throttle-limiter and throttle-lock versions on the SR 430/SR 450.

For spraying work, the earlier discharge-rate tables distinguish pump, nozzle, and baffle-screen configurations. Pressure-pump hose-layout views identify the supply and return connections. The SR 450 receives separate procedures for its metering unit, rotary shutter, operating cable, and antistatic wire and chain.

Fuel handling and ignition testing involve flammable gasoline and high voltage; follow the applicable manual’s safety precautions.

A Preview of Bearing, Ignition and Metering Specifications

For BR 320/BR 400 and SR 320/SR 400, the torque table specifies 25 Nm for the flywheel nut. Crankshaft installation calls for heating the bearing inner races to approximately 150°C (300°F).

Ignition specifications for the same family list primary coil winding resistance at 0.8–1.3 ohms.

The SR 320/SR 400 metering table lists 3.6 L/min at knob position 6 without the pressure pump or baffle screen, alongside separate figures for other equipment configurations.