This document is a service manual for the STIHL Series 4137 Components HT, providing detailed instructions for repair and servicing procedures. It covers various components of the device, including the engine, fuel system, throttle control, drive tube, and rewind starter.
Function Description
The STIHL Series 4137 Components HT is a powerhead designed for use with various attachments, such as the HT 70 and HT 75 models, which are likely pole pruners or similar long-reach tools. The manual details the repair and maintenance of its core components, ensuring the device operates efficiently and safely. Key functions include:
- Engine Operation: The engine provides the power for the device. The manual covers troubleshooting, removal, installation, and repair of engine components like the shroud, clutch, clutch drum, muffler/spark arresting screen, and the engine itself.
- Fuel System Management: The fuel system delivers fuel to the engine. The manual describes the air filter, carburetor, leakage test, spacer flange, flange mounting with oval and square end covers, metering diaphragm, inlet needle, fixed jet, pump diaphragm, and fuel tank/fuel hoses. It also covers adjustments for carburetors with one, two, or limiter cap screws.
- Throttle Control: This system regulates engine speed. The manual details different throttle control versions (up to 1997, up to 2001, and from 2002), including the throttle trigger/interlock lever, slide control, and throttle cable.
- Rewind Starter: This mechanism is used to start the engine. The manual provides instructions for general maintenance, removal, installation, rope rotor/rewind spring, tensioning, starter rope, starter grip, and carrier/pawl.
- Drive Tube: This component transmits power from the engine to the attachment. The manual covers the drive shaft/flexible liner (for HT 70) and telescopic drive tube (for HT 75), including removal, installation, and disassembling procedures.
- AV System: The anti-vibration system reduces vibrations during operation, enhancing user comfort. The manual includes repair instructions for this system.
Important Technical Specifications
- Carburetor Type: Diaphragm carburetor.
- Carburetor Leakage Test at Gauge Pressure: 80 kPa (0.8 bar).
- Fuel Mixture: Regular brand-name gasoline (min. 90 RON) with STIHL 50:1 two-stroke engine oil. Refer to the instruction manual for further details.
- Rated Idle Speed: 2,800 rpm.
- Rated Cut-off Speed: 10,500 rpm.
- Operation of Tank Vent:
- At gauge pressure: 50 kPa (0.5 bar).
- Under vacuum: 20 kPa (0.2 bar).
- Tightening Torques: Specific torque values are provided for various fasteners, including screws, nuts, and bolts, ranging from 0.37 Nm to 26.0 Nm. For example:
- Control handle molding (outer/inner) screw: 1.0 Nm.
- Control handle clamp/drive tube screw: 5.0 Nm.
- Muffler/cylinder screw: 11.5 Nm.
- Clutch carrier/flywheel/crankshaft screw: 26.0 Nm.
- Spark plug: 20.0 Nm.
- Power Screwdriver Settings for Polymer:
- Plastoform screws: max. 600 rpm.
- DG screws: max. 500 rpm.
- Drive Tube Dimensions (HT 70): The drive shaft must be pushed into the drive tube until dimension "a" is 17 mm.
- Drive Tube Dimensions (Telescopic): The drive shaft must be pushed into the outer drive tube until dimension "a" is 11 mm.
- Inner Spring Bore Distance: The distance of the inner spring bore from the bore and correct if necessary. Dimension "a" must be 2 mm.
Usage Features
The manual emphasizes safety and proper handling during repair and maintenance.
- Safety Precautions: Gasoline is extremely flammable, and all work with fuel must be performed outdoors. Spilled fuel must be wiped away immediately. Always observe local and country-specific safety regulations.
- Special Servicing Tools: The manual lists specific tools required for various tasks, such as locking strips, pullers, hooks, drifts, and torque wrenches. Using original STIHL replacement parts is always recommended.
- Troubleshooting Guides: Detailed tables are provided for common issues, their causes, and remedies for components like the clutch, rewind starter, fuel system, and engine.
- Carburetor Adjustment: Instructions are given for adjusting carburetors with two adjusting screws or a limiter cap, including standard settings for idle speed and high-speed screws.
- Drive Tube Installation: The drive shaft should be coated with STIHL gear lubricant before insertion into the flexible liner. The drive shaft must be pushed home until the clip is seated in the stop or mounting rivet, and the end should be visible.
- Rewind Starter Tensioning: The rewind spring should be carefully tensioned to avoid over-tensioning, which can cause damage.
Maintenance Features
The manual provides comprehensive maintenance instructions for various components.
- Cleaning: Regular cleaning of the air filter, spark arresting screen, and fuel tank is crucial for optimal performance.
- Lubrication: Specific lubricants are recommended for different parts, such as STIHL special lubricating oil for the rope rotor bore, STIHL shaft grease for the drive shaft, and STIHL Press Fluid OH 723 for the rubber element in the AV sleeve.
- Part Replacement: Instructions are given for replacing worn or damaged parts, including clutch shoes, springs, rewind springs, fuel filters, diaphragms, and drive tube components.
- Leakage Tests: Procedures for checking carburetor and tank vent leakage are detailed to ensure proper fuel system function.
- Adjustments: Detailed steps are provided for adjusting the throttle cable, idle speed, and high-speed screws on the carburetor to ensure correct engine operation.
- Inspection: Regular inspection of components like the clutch drum for wear marks, metering diaphragm for fatigue, and drive shafts for distortion or damage is recommended.
- Assembly and Disassembly: Clear, step-by-step instructions with illustrations are provided for disassembling and reassembling all major components in the reverse sequence of removal.
- Threadlocking Adhesive: Medium-strength and high-strength threadlocking adhesives (Loctite 242, 270, 649) are specified for certain applications to secure fasteners.
- Sealants: Dirko HT red sealant is recommended for crankcase and oil seals.
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