STIH) Technical Information 8.20 New chain saws STIHL MS 20 T, MS 20 TC Series 45 Summary. Technical description 2. Specifications 3. Service accessories and special tools 4. Servicing 5. Spare parts 6. Repair times englisch / English
Page 2 Technical Information 8.20 The new STIHL MS 20 T tree surgery chain saw with its new, low-emission, efficient 2-Mix engine with stratified scavenging replaces the predecessor model MS 200 T. The new MS 20 T is used in professional applications in municipal services, tree maintenance operations, gardening and landscaping operations and road maintenance depots. Its main advantages are in cutting thick and long branches branches to length, crown reduction and removing deadwood, as well as felling in special situations. The STIHL MS 20 T offers impressively high lugging power despite its low weight. The new antivibration system transmits minimal vibration to the user while preserving the usual control and rigidity. In conjunction with the new 3/8" PS3 saw chain with full chisel cutters, these characteristics permit precise cutting an important advantage in tree maintenance. The following features make it exceptionally easy to use: Captive nut on chain sprocket cover Loss-proof chain scabbard Improved filter life Fuel cap openable without tools Transparent fuel tank Microprocessor-controlled ignition system for jerk-free starting Despite the compact design, the MS 20 T is a snap to service. All service-related components are accessible in a few easy steps. In addition to the standard version, the deluxe version MS 20 TC with ErgoStart and manual fuel pump is available in some markets. Tree surgery chain saws are only to be used by trained tree surgery professionals. They are not for classic tree felling or cutting firewood. Regional safety regulations must be observed.. Technical description. Interior sprocket The internal sprocket reduces the distance between the handle and cutting plane. This optimizes the balance and handling of the machine..2 Chain sprocket cover with captive nut The nut is integrally connected to the chain sprocket cover; the nut cannot be lost. When fitting the chain sprocket cover the nut is always in the correct position and cannot skew. 002TI00 KN 002TI002 KN
Technical Information 8.20 Page 3.3 Loss-proof chain scabbard The loss-proof chain scabbard is designed especially for the demands posed by working in trees. It stands out because of the following features:.4 Adjustable oil pump 3 2 Rings () For fastening the chain scabbard to the user's harness Always use the pull-out ring on the back of the chain saw to transport and secure the chain saw on a rope. Never use the chain scabbard rings to transport or secure the chain saw risk of accident due to falling chain saw! 002TI003 KN The delivery rate is adjustable for various types of wood and guide bar lengths. The adjusting screw () is infinitely adjustable with the combination wrench (max. /4 turn)..5 Winter operation The MS 20 T is equipped with a carburetor heating system. With the carburetor heating system, it is possible to route heated cooling air over the carburetor. This prevents carburetor icing under winter conditions. To this end, there is a shutter under the chain sprocket cover that can be set to the right for winter operation and to the left for summer operation. 002TI004 KN Locking lug (2) The chain scabbard is connected securely to the chain sprocket cover of the machine Prevents possible falling of the chain scabbard when the machine is hoisted into the tree Always slide the chain scabbard onto the guide bar until it engages locking lug (2) must snap into the sprocket cover. Broad base (3) for covering the spiked bumper Prevents possible injury to users and trees by the spikes of the spiked bumper Prevents damage to material, e. g., ropes or slings Shutter to the left Summer operation: At temperatures above +20 C Shutter to the right Winter operation: At temperatures below +0 C 002TI005 KN
Page 4 Technical Information 8.20.6 Service-friendly design All service-relevant components are accessible in a few steps. Accessing the air filter Fanwheel side 2. Remove fanwheel cover (unscrew four screws) Direct access to ignition module (), flywheel (2) and starter in fanwheel cover. 002TI006 KN. Remove carburetor box cover () (no tools required) Accessing the carburetor 2 3 002TI008 KN Sprocket side 2 002TI04 KN. Remove the chain sprocket cover Direct access to muffler (), chain sprocket (2), clutch (3) and chain tensioner (4) 3 4 002TI007 KN. Remove carburetor box cover and air filter. Remove screws () lightweight screws. Remove baffle (2) and filter base (3) During assembly, observe the tightening torque for the lightweight screws: 0.8 Nm (stage ), 3 Nm (stage 2)
Technical Information 8.20 Page 5 2. Specifications 2. Engine Single cylinder two-stroke engine Carving guide bars Bar lengths (/4" pitch): Groove width: 25, 30 cm.3 mm Displacement: 35.2 cm 3 Bore: 40 mm Stroke: 28 mm Engine power to ISO 7293:.8 kw (2.4 HP) at 9500 rpm Idle speed: 3000 rpm Maximum permissible 4000 rpm speed with bar and chain: Saw chains 3/8"Picco Picco Micro Comfort 3 (63 PMC3) Pitch: 3/8"P (9.32 mm) Drive link gauge:.3 mm Picco Super 3 (63 PS3) Pitch: Drive link gauge: 3/8"P (9.32 mm).3 mm 2.2 Ignition system Electronic magneto ignition (breakerless) Spark plug (suppressed): NGK CMR 6 H Electrode gap: 0.5 mm Picco Duro 3 (63 PD3) Pitch: Drive link gauge: 3/8"P (9.32 mm).3 mm 2.3 Fuel system All position diaphragm carburetor with integral fuel pump Fuel tank capacity: 2.4 Chain lubrication Fully automatic, speed-controlled oil pump, additional manual oil flow control Oil tank capacity: 0.3 l 0.22 l Saw chains /4" Use saw chain only in combination with the carving guide bars Rapid Micro Spezial (3 RMS) Pitch: Drive link gauge: Chain sprockets 6-tooth for 3/8"P (spur chain sprocket) 8-tooth for /4" (spur chain sprocket) /4" (6.36 mm).3 mm 2.5 Weight dry, without bar and chain MS 20 T: MS 20 TC: 3.7 kg 3.8 kg 2.6 Cutting attachment Rollomatic guide bars Cutting length (3/8" pitch): Groove width: 30, 35, 40 cm.3 mm
Page 6 Technical Information 8.20 3. Service accessories and special tools 3. Service accessories Designation Part number Use Set of carburetor parts 45 007 700 Carburetor repairs Locking strip 45 893 5900 Blocking the crankshaft for removal of chain sprocket and clutch Grease (225 g tube) 078 20 Oil seals, oil pump drive, sprocket bearings, chain tensioner Bearing and sliding surfaces for throttle trigger, brake lever and trigger lockout STIHL special lubricant 078 47 35 Bearing bore in rope rotor, rewind spring in fan housing Standard commercially available CFC and HFC-free solvent-based degreasing agent Cleaning crankshaft stub and cone on flywheel 3.2 Special tools 3.2. To be procured for the STIHL MS 20, MS 20 T Designation Part number Use Flange 590 850 4203 Engine leakage test, inlet side Installing sleeve 45 893 4600 Protecting the oil seal when pushing it onto the shaft 3.3 Existing special tools The available special tools are listed in the Service Manual for the STIHL MS 20, MS 20 T. 3.3. Rework information concerning flange (for engine leakage test, outlet side) Flange 590 855 420 replaces the previous flange 4224 893 250. The previous flange 4224 893 250 can be reworked to bring it up to the current status according to the following drawing. 39,25 mm 35 mm 002TI0 KN
Technical Information 8.20 Page 7 4. Servicing 4. Removing chain sprocket / clutch new locking strip When removing and installing the chain sprocket an clutch, a locking strip is required for blocking the crankshaft. A new locking strip is being introduced with the MS 20 T. It is included with the replacement chain sprocket or is available separately under the part number 45 893 5900. The new geometry of the locking strip makes it much easier to position within the cylinder. The locking strip can be pushed into the inside of the cylinder directly through the spark plug opening. Fastening the locking strip on the cylinder fin ensures that it is always positioned correctly inside the cylinder.. Unscrew the spark plug. Turn the clutch until the piston is set to bottom dead center 002TI02 KN 4.2 Carburetor adjustment without limiter cap 4.2. New limiter cap To comply with various national and international exhaust laws and regulations, the new generation of limiter caps is used in the MS 20 T as already in the MS 26, MS 27 and MS 29. Use of the new limiter cap is described in TI 8.200 and TI 25.200 respectively. 4.2.2 Removing the limiter cap. Screw the puller 590 890 4502 (special tool) counterclockwise (left-hand thread) about five turns into the limiter cap. Remove the limiter cap. Use the screwdriver (590 890 2306) to unscrew the high speed screw (H) with the plastic segment. Insert the locking strip through the opening as far as it will go into the cylinder 002TI03 KN 002TI05 KN. Fasten the locking strip to the cylinder fin. Turn the clutch clockwise until the piston rests against the locking strip
Page 8 Technical Information 8.20 4.2.4 Fitting the limiter cap on the high speed screw. If the high speed screw (H) is going to be reused, remove the plastic insert Do not re-install the used cap, since it is damaged during removal. Service work on metering diaphragm, pump diaphragm, inlet needle, lever, gaskets, choke shutter as previously. Do not dismantle the choke shutter, as otherwise the factory default setting will no longer be correct and this can lead to impaired engine performance. 5902TI08 KN. Orient the new limiter cap () so that the notch (arrow) points vertically upward. Press the limiter cap () onto the high speed screw (H) until it engages in the first position nearly flush with the dome (arrow) do not press it in all the way 002TI06 KN 4.2.3 Basic setting After servicing or replacement of the adjusting screws, it is necessary to perform a basic setting of the carburetor.. Check the air filter clean or replace it if necessary. Check the spark arresting screen in the muffler (present only in some countries) clean or replace it if necessary The following screwdrivers should be used for the basic setting. Low speed screw L Flat head screwdriver 590 890 2305 High speed screw H Screwdriver 590 890 2306 with hex blade SW 2. Carry out basic setting of the adjusting screws set adjusting screw by turning counterclockwise starting with the screws firmly seated Low speed screw L: High speed screw H: turn open 2 turns open
Technical Information 8.20 Page 9 4.2.5 Adjustment Let the engine warm up before starting adjustment. Afterwards, allow the engine to idle for 20 seconds. Do not make any adjustments during this time! The ignition system adjusts the idling characteristics 4.2.6 Checking the position of the limiter cap Adjust the specified engine speeds within a tolerance range of +/- 200 rpm as follows. Set speed to 2800 rpm with idle speed adjusting screw (LA) 2. Turn the low speed screw (L) clockwise or counterclockwise to set the highest speed. If this speed is greater than 3300 rpm, stop and start again with step. 3. Set the speed to 3300 rpm again with idle speed adjusting screw (LA) 4. Set the speed to 2800 rpm (counterclockwise) with low speed screw (L) 5. Set the speed to 3000 rpm with idle speed adjusting screw (LA) 6. Set the speed to 4000 rpm with the high speed screw (H) (starting from the standard setting) Once the maximum speed of 4000 rpm is reached, do not continue to make the mix leaner the ignition module limits the maximum speed to 4000 rpm. The permissible maximum speed cannot be increased by continuing to make the mix leaner. Making the setting too lean increases the risk of engine damage. 7. Check the position of the limiter cap and secure the limiter cap on the high speed screw. The notch (arrow) on the limiter cap () must point vertically upward If the notch (arrow) on the limiter cap () does not point vertically upward:. Use a screwdriver to turn the limiter cap () as far as it will go counterclockwise notch (arrow) points upward. Continue with "Securing the limiter cap on the high speed screw" 002TI08 KN 002TI09 KN
Page 0 Technical Information 8.20 4.2.7 Securing the limiter cap on the high speed screw Notes regarding press fluid OH 723 Press fluid OH 723 produces a lubricant film that simplifies assembly. The lubricant evaporates after a short time the hose is firmly seated. Never use fuel, oil or grease as a lubricant. Fuel, oil and grease do not evaporate the hose may come loose.. Use a drift (diameter 6 mm) through the opening (arrow) to push the limiter cap until it is against the adjusting screws the limiter cap is seated approx. 2 mm inside the carburetor housing limiter cap is secured 4.3 Fuel system barbed connectors To ensure the leakproofness of the fuel system:. Pull or push the fuel hoses, by hand whenever possible, in the direction of the connector in order to avoid damage to the barbed connector sharp-edged pliers, screwdrivers, etc., may not be used also, do not cut open fuel hoses with a knife or similar aids. Do not reuse fuel hoses after disassembly, but instead always replace them with new hoses fuel hoses can be overstretched when being detached. Mount new fuel hoses dry or using press fluid OH 723 078 957 9000. Other press fluids are not permitted and may lead to fuel hose damage. When using press fluid OH 723, apply press fluid OH 723 to the ends of the hose and the connectors and press the new hoses onto the barbed connectors 002TI020 KN 4.4 Carburetor adjustment with limiter cap With this carburetor, the high speed screw H can be adjusted by the user within a range of an approx. 3/4 turn. Using a standard carburetor screwdriver, carry out standard adjustment with limiter cap on the high speed screw.. Switch off the engine. Check the air filter clean or replace it if necessary. Check the spark arresting screen in the muffler (present only in some countries) clean or replace it if necessary. Turn the high speed screw (H) counterclockwise as far as possible (max. 3/4 turn). Carefully turn the low speed screw (L) clockwise as far as possible, then back off turn. H L 002TI022 KN
Technical Information 8.20 Page 4.4. Setting the idle speed Engine stops when idling. Set low speed screw (L) to standard setting 002TI023 KN Erratic idling behavior poor acceleration Let the engine warm up before starting adjustment. Afterwards, allow the engine to idle for 20 seconds. Do not make any adjustments during this time! The ignition system adjusts the idling characteristics. Set low speed screw (L) to standard setting. Idle speed setting is too lean turn the low speed screw (L) counterclockwise until the engine runs and accelerates smoothly.. Whenever the low speed screw (L) has been adjusted, at least one adjustment must also be made on the idle speed screw (LA).. Turn the idle speed adjusting screw (LA) clockwise until the saw chain begins to run then turn it back /2 turns. Saw chain rotates at idle speed Let the engine warm up before starting adjustment. Afterwards, allow the engine to idle for 20 seconds. Do not make any adjustments during this time! The ignition system adjusts the idling characteristics. Set low speed screw (L) to standard setting. Turn the idle speed screw (LA) counterclockwise until the chain stops running then turn another /2 turns in the same direction. If the saw chain continues to keep rotating in idle even after adjustment, repair the chain saw. Adjustment for use in the mountains or at sea level A marginal adjustment may be necessary if the engine does not run satisfactorily in mountain country or at sea level:. Check the standard setting. Let the engine warm up In the mountains. Turn the high speed screw (H) slightly clockwise (leaner) max. up to the stop. If you make the setting too lean it will increase the risk of engine damage through lack of lubrication and overheating. At sea level. Turn the high speed adjusting screw (H) slightly counterclockwise (richer) max. up to the stop
Page 2 Technical Information 8.20 5. Spare parts The repair times are specified in minutes. The spare parts list for the models MS 20 T and MS 20 TC will be available when they are launched on the market. Repair activity MS 20 T 5. Tightening torques The tightening torques are listed in the Service Manual for the STIHL MS 20, MS 20 T. 5.2 Serial number The serial number is on the tank housing below the hand guard. 6. Repair times The specified repair times apply for trained and qualified personnel as well as for properly equipped repair shops. The repair times are specified in minutes. The table of repair times can be added to the STIHL table of repair times. 002TI02 KN Crankcase, engine pan, pressure 40 test* 2 Crankshaft, bearings, pressure 40 test* 3 O-rings, pressure test* 60 4 Test crankcase for leaks, trial run 35 5 Cylinder, piston, pressure test* 70 6 Ignition system, contact* 25 7 Fuel supply, tank vent, trial run 20 8 Manifold or flange, pressure test 40 9 Carburetor, test* 25 0 Tank housing with trial run 30 Oil supply 20 2 Oil pump, trial run 20 3 Handle frame, handle tube, 45 handle housing, shroud with trial run in each case 4 Starter mechanism with trial run 20 5 Clutch, trial run 20 6 Chain brake, trial run, function test 25 with bar and chain 7 Muffler 5 8 Air filter 5 9 Master Control lever and/or stop 45 switch with trial run * Trial run under load ANDREAS STIHL AG & Co. KG, 20 Technical Documentation D/MTK-ni