Stihl BG 85 Parts Manual

The Stihl BG 85 is a professional-grade backpack blower designed for demanding commercial and residential applications. This parts manual provides detailed diagrams, part numbers, and ordering information for the complete assembly, engine, fuel system, ignition, air filtration, cooling, exhaust, starter, and housing components. Below are key sections for identification, engine parts, assembly groups, maintenance, and ordering.

1. Product Identification & Specifications 2. Safety Information 3. Engine Assembly & Crankcase 4. Fuel System Components 5. Ignition System & Electronics 6. Air Filtration & Cooling System 7. Exhaust System & Muffler 8. Starter Assembly & Rewind 9. Blower Housing & Tube Assembly 10. Harness & Control Parts 11. Maintenance & Torque Specifications 12. Parts Ordering & Exploded Diagrams

Product Identification & Specifications

Key identifiers: Model BG 85, Engine type: 2-stroke, single-cylinder, air-cooled. Locate serial number on crankcase.

SpecificationDescription
Engine Displacement28.4 cc (1.73 cu. in.)
Power Output0.9 kW (1.2 bhp) at 7500 rpm
Idle Speed2800 rpm
Max. Air Speed83 m/s (186 mph)
Air Volume750 m³/h (441 cfm)
Fuel/Oil Mix Ratio50:1 (ISO-L-EGD, JASO FD, API TC)
Dry Weight8.9 kg (19.6 lbs)
Sound Power Level112 dB(A)
Vibration Level (left/right)4.5/5.5 m/s²

Safety Information

Always stop engine before inspecting or replacing parts. Use genuine Stihl parts only.

  1. Disconnect spark plug boot to prevent accidental starting.
  2. Allow engine to cool before working on muffler or cylinder.
  3. Use proper tools and follow torque specifications.
  4. Replace safety-critical parts (e.g., fuel lines, ignition components) with OEM parts.

WARNING! Operating without proper guards or with worn parts can cause serious injury. Always wear protective equipment.

Engine Assembly & Crankcase

Includes cylinder, piston, crankshaft, bearings, seals, and crankcase halves.

  1. Cylinder: Part # 1128 020 2001 (with decompression valve).
  2. Piston: Part # 1128 030 2000 (including rings and wrist pin).
  3. Crankshaft: Part # 1128 040 2001.
  4. Crankcase (upper/lower): Part # 1128 050 2000 / 1128 050 2001.
  5. Crankcase gasket: Part # 1128 050 2002.
  6. Main bearings & seals: Refer to diagram for specific locations.

CAUTION! Ensure crankcase halves are sealed properly to prevent air leaks affecting engine performance.

Fuel System Components

Ignition System & Electronics

Access components by removing blower housing. Includes ignition module, spark plug, stop switch, and wiring.

Ignition Module: Part # 1128 400 2001 (with advance curve). Spark Plug: Bosch WSR 6 F or equivalent, gap 0.5mm. Stop Switch: Part # 1128 992 2000. Spark Plug Boot: Part # 1128 992 2001. Wiring Harness: Part # 1128 992 2002 (complete).

Air Filtration & Cooling System

Air filter: Part # 1128 140 2000 (pre-cleaner foam). Filter cover: Part # 1128 140 2001.

  1. Remove cover screw to access filter.
  2. Clean foam filter in warm, soapy water; air dry.
  3. Re-oil lightly with Stihl filter oil (Part # 0000 350 3200).
  4. Cooling fan: Part # 1128 050 2003 (attached to crankshaft).
  5. Fan shroud: Part # 1128 050 2004.

Tip: A clogged air filter is a common cause of power loss and overheating.

Exhaust System & Muffler

Supports standard muffler with spark arrestor screen.

  1. Muffler Assembly: Part # 1128 145 2000.
  2. Muffler Gasket: Part # 1128 145 2001 (cylinder interface).
  3. Spark Arrestor Screen: Part # 1128 145 2002 (clean regularly).
  4. Muffler Cover: Part # 1128 145 2003.
  5. Mounting Screws/Nuts: Refer to hardware list.

WARNING! Muffler gets extremely hot. Always handle with gloves after cooling. Ensure spark arrestor is clean and intact for safe operation.

Starter Assembly & Rewind

Starter housing: Part # 1128 070 2000. Starter pulley: Part # 1128 070 2001. Starter rope: Part # 1128 070 2002 (1.8m x 3mm). Recoil spring: Part # 1128 070 2003. Starter handle: Part # 1128 070 2004.

Blower Housing & Tube Assembly

Unplug before cleaning. Inspect for cracks, especially at mounting points.

Main Housing: Part # 1128 850 2000. Air Tube: Part # 1128 850 2001. Tube Locking Collar: Part # 1128 850 2002. Nozzle: Part # 1128 850 2003. Harness Mounting Brackets: Part # 1128 850 2004 (set).

CAUTION! Do not operate with damaged housing or loose tubes, as this affects performance and safety.

Harness & Control Parts

Backpack harness: Part # 1128 850 2005 (includes shoulder straps and waist belt). Throttle trigger: Part # 1128 992 2003. Throttle cable: Part # 1128 992 2004. Throttle lock: Part # 1128 992 2005. Master control lever (STOP/CHOKE/RUN): Part # 1128 992 2006.

Maintenance & Torque Specifications

ComponentTorqueNotes
Cylinder bolts (M6)10 Nm (88 in-lb)Cross-tighten in sequence
Crankcase bolts (M5)6 Nm (53 in-lb)Apply sealant to gasket
Muffler nuts (M6)8 Nm (71 in-lb)Replace gasket each time
Fan/flywheel nut (M10)40 Nm (30 ft-lb)Use holder tool
Spark plug20 Nm (15 ft-lb)Do not over-tighten
Starter housing screws4 Nm (35 in-lb)Plastic threads

Maintenance Intervals: Clean air filter every 10 hours. Replace fuel filter annually. Check spark arrestor monthly under heavy use.

Parts Ordering & Exploded Diagrams

Use the official Stihl IPL (Illustrated Parts List) for BG 85, reference document # 9 898 085 01. Diagrams show assembly groups with call-out numbers matching part numbers.

  1. Identify the assembly group (e.g., 1100 for engine, 1400 for air filter).
  2. Locate the item number on the diagram.
  3. Cross-reference with the parts list table for the correct part number.
  4. Order through authorized Stihl dealers only.

Reset: After major service, reset ECU by disconnecting spark plug and pulling starter 5 times.

Service & Support: Contact authorized Stihl servicing dealer. For dealer locator: www.stihlusa.com or call 1-800-467-8445.

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