Stihl MS 661 Manual
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Stihl MS 661 Manual

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STIH)
STIHL MS 661, 661 C-M
2013-07

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Summary of Contents for Stihl MS 661

  • Page 1 STIH) STIHL MS 661, 661 C-M 2013-07...

  • Page 2: Table Of Contents

    Rewind Spring Replacing the Muffler Rewind Spring Leakage Test Segment 6.2.1 Preparations 6.2.2 Vacuum Test 6.2.3 Pressure Test Oil Seals 6.3.1 Ignition Side 6.3.2 Clutch Side Shroud Cylinder © ANDREAS STIHL AG & Co. KG, 2013 MS 661, MS 661 C-M...
  • Page 3 Tank Vent Oil Pumps 13.10.1 Testing 12.4 Valve 13.10.2 Removing and Servicing Aids Installing 13.11 Fuel Intake 13.11.1 Pickup Body 13.11.2 Fuel Suction Hose in Tank Housing 13.11.3 Fuel Suction Hose on Carburetor 13.11.4 Tank Housing MS 661, MS 661 C-M...

  • Page 4: Introduction And Safety Precautions

    Always use original STIHL descriptions are listed in the chapter replacement parts. on "Special Servicing Tools" in this They can be identified by the STIHL manual. Use the part numbers to part number, identify the tools in the the STIH) "Special Tools"...
  • Page 5 Install new fuel hoses either dry or 5910 890 4000 to press electrical burns or other serious injuries. with the aid of STIHL press fluid wires fully into their guides. – coat the ends of hoses and the Always replace damaged parts.

  • Page 6: Specifications

    Specifications Engine MS 661, MS 661 C-M Displacement: 91.1 cc Bore: 56.0 mm Stroke: 37.0 mm Engine power to ISO 7293: 5.4 kW (7.4 bhp) at 9,500 rpm Max. permissible speed (with cutting 13,500 rpm attachment): Idle speed: 2,800 rpm...

  • Page 7: Tightening Torquese

    Spiked bumper / chain sprocket cover Screw M 5x12 Spiked bumper / chain sprocket cover / nut Screw M 5x12 Spiked bumper / crankcase, top 4), 6) Locknut Spiked bumper / crankcase, top / nut MS 661, MS 661 C-M...
  • Page 8 2) Loctite 270, high strength 3) Loctite 272, high strength up to 250°C 4) Screws with binding head 5) Micro-encapsulated screws 6) Waxed screws 7) Degrease crankshaft / flywheel and mount oil-free W) Heated handles V) Carburetor heating MS 661, MS 661 C-M...

  • Page 9: Troubleshooting

    Replace the clutch springs Loud noises Clutch springs stretched Replace all clutch springs Needle cage damaged Fit new needle cage Clutch shoe retainer broken Install new retainer or clutch Clutch shoes and carrier worn Install new clutch MS 661, MS 661 C-M...

  • Page 10: Chain Drive, Chain Brake, Chain

    Saw chain does not stop Chain brake spring Fit new brake spring immediately when brake is stretched / broken activated Brake band Fit new brake band stretched / worn / broken Clutch drum worn Install new clutch drum MS 661, MS 661 C-M...

  • Page 11: Chain Lubrication

    Oil pump damaged or worn Install new oil pump Oil pump delivery rate set too low Adjust oil pump Worm driver is loose Install new worm Sealing ring between oil pump and Replace the sealing ring crankcase damaged MS 661, MS 661 C-M...

  • Page 12: Rewind Starter

    (spring windings degreasant (containing no stick together) or moisture has got chlorinated or halogenated onto the rewind spring (spring hydrocarbons), then pull rope windings frozen together) carefully several times until normal action is restored MS 661, MS 661 C-M...

  • Page 13: Ignition System

    Check operation of spark plug, clean the spark plug, replace if necessary, check M-Tronic with aid of troubleshooting chart, b 8.7. The carburetor or engine may also be the cause of poor engine running behavior MS 661, MS 661 C-M...

  • Page 14: Carburetor

    Low speed screw L and / or high Check basic carburetor setting, speed screw H too lean correct if necessary Models with M-Tronic, carburetor Check M-Tronic with STIHL MDG 1 setting too lean and troubleshooting chart, b 8.7, adjust or calibrate control unit, b 8.1...
  • Page 15 Readjust idle speed screw incorrect – throttle shutter LA (clockwise) completely closed Models with M-Tronic, carburetor Check M-Tronic with STIHL MDG 1 setting too rich or too lean and troubleshooting chart, b 8.7, adjust or calibrate control unit, b 8.1...
  • Page 16 Engine idle speed too high Readjust idle speed screw idling LA (counterclockwise) Models with M-Tronic, idle speed Check M-Tronic with STIHL MDG 1 too high and troubleshooting chart, b 8.7, adjust or calibrate control unit, b 8.1 (setting of idle speed screw must...
  • Page 17 Check carburetor and choke shaft, no power and a very low maximum service or replace if necessary speed Models with M-Tronic, carburetor Check M-Tronic with STIHL MDG 1 setting too rich and troubleshooting chart, b 8.7, adjust or calibrate control unit, b 8.1...

  • Page 18: Engine

    Insufficient cylinder cooling. Air Thoroughly clean all cooling air inlets in fan housing blocked or openings and the cylinder fins cooling fins on cylinder very dirty Air inlet in fan housing dirty Clean air inlet on fan housing MS 661, MS 661 C-M...

  • Page 19: Clutch

    – Pull off the boot and unscrew the cylinder. spark plug. – Reassemble all other parts in the – Remove the rim sprocket and reverse sequence. clutch drum. : Use hook (2) 5910 890 2800 to remove the clutch springs (1). MS 661, MS 661 C-M...

  • Page 20: Chain Brake

    : Take out the screw (1) and pry the brake band (2) out if its seat (arrow). Do not overstretch the brake band. – Disengage the chain brake. MS 661, MS 661 C-M...

  • Page 21: Brake Lever

    – Reassemble all other parts in the lever (3) off the pivot pins reverse sequence. together. – Check the pivot pins, replace if necessary, b 5.5 – Inspect the cam lever and replace if necessary, b 5.4 MS 661, MS 661 C-M...

  • Page 22: Cam Lever

    – Remove the cam lever, b 5.4 brake lever (2) and use the assembly tool (3) 1117 890 0900 – Fit the E-clip- to attach it to the anchor pin. – Reassemble all other parts in the reverse sequence. MS 661, MS 661 C-M...

  • Page 23: Chain Tensioner

    (2) is visible. : Take out the screw (2) and pull out the tensioner (3). – Remove the O-ring. – Check individual parts of the chain tensioner, replace if necessary MS 661, MS 661 C-M...

  • Page 24: Bar Mounting Studs

    : Fit the O-ring in the spur gear recess (arrow). – Clean all disassembled parts, b 16 – Lubricate the threads, gears and O-ring with STIHL grease, b 16 : Push the new collar nuts (1) into position. – Reassemble in the reverse sequence.

  • Page 25: Engine

    Always replace components with : Insert and tighten down the damaged sealing faces. screws (2) firmly. : Remove the gasket (1) and take out the screws (2) – always install a new gasket. MS 661, MS 661 C-M...

  • Page 26: Leakage Test

    : Fit the sealing plate (1) 0000 855 8106 on the exhaust port – between the gasket / heat shield and cylinder. – Tighten the screws moderately. The sealing plate must completely fill the space between the two screws. MS 661, MS 661 C-M...

  • Page 27: Vacuum Test

    Carry out the same preparations as – Replenish threadlocking for the vacuum test, b 6.2.2 adhesive and install the muffler, b 6.1 – Install the carburetor, b 13.4 – Reassemble all other parts in the reverse sequence. MS 661, MS 661 C-M...

  • Page 28: Clutch Side

    16 – Clean the sealing face. – Reassemble all other parts in the reverse sequence. – Lubricate sealing lips of new oil seal with STIHL grease, b 16 Take care not to damage the crankshaft stub. 6.3.2 Clutch Side –...

  • Page 29: Shroud

    (special tool). firmly. – Remove the shroud, b 6.4 – Coat grommet with STIHL press fluid and fit its small diameter – Remove the rewind starter, over the stud's washer, b 16 b 9.2...
  • Page 30 – Coat the inside of the manifold the washer in the manifold. with STIHL press fluid, b 16 : Fit the hose clamp (3) – the : Insert new washer (1) through screw (4) must be next to the larger diameter of manifold (2) as rib (5).
  • Page 31 – they might otherwise break. : Tighten down the screws (1) through the holes (arrows) in the : Slide the cylinder over the piston, cylinder in a crosswise pattern. the clamping strap moves downwards at the same time. MS 661, MS 661 C-M...

  • Page 32: Crankshaft

    Use the tools in the service tool set – Reassemble all other parts in the 5910 007 2222 to remove and reverse sequence. install the clutch side of the crankcase : Remove the retaining ring (1). MS 661, MS 661 C-M...
  • Page 33 (2) butts against the crankcase – left-hand thread. : Remove the gasket (1). : Fit the plate (2) 5910 893 2101 against the ignition side of the crankcase so that the number "31" (arrow) is at the bottom. MS 661, MS 661 C-M...
  • Page 34 (3) of the connecting rod always points upward to the cylinder. – Remove the installing tool. : Position the screw sleeve (2) 5910 893 2421 on the crankshaft thread (1) and screw it into place. MS 661, MS 661 C-M...
  • Page 35 : Position the clutch side of the : Turn the spindle (2) crankcase on the straight counterclockwise until the crankshaft stub and the screws crankcase locates against the and push it on as far as stop. guide sleeves. MS 661, MS 661 C-M...

  • Page 36: Bearings / Crankcase

    – Install the oil seals, b 6.3 – See also Troubleshooting, – Fit the retaining ring at the clutch b 3.7 side. – Remove the crankshaft, b 6.6 – Check and install the piston, b 6.7 MS 661, MS 661 C-M...

  • Page 37: Piston

    – Check and clean the crankcase home until it butts against the oil or replace if necessary. pump : Pry hookless snap ring out of boss at ignition side – apply tool to recess (arrow). MS 661, MS 661 C-M...
  • Page 38 : Pull out the needle cage (1), – Install the cylinder, b 6.5 inspect and clean it, replace if – Prepare snap ring for installation necessary. with installing tool – Reassemble all other parts in the 5910 890 2212. reverse sequence. MS 661, MS 661 C-M...

  • Page 39: Piston Rings

    – they might otherwise break. – Tighten down the decompression valve firmly. – Install the piston, b 6.7 – Reassemble all other parts in the – Reassemble all other parts in the reverse sequence. reverse sequence. MS 661, MS 661 C-M...

  • Page 40: Ignition System

    A new ignition module b 9.2 must be installed if no ignition spark is obtained (after checking that wiring and stop switch are in good – Remove the filter cover and pull condition). off the spark plug boot. MS 661, MS 661 C-M...
  • Page 41 – Rotate the flywheel and make sure it does not touch the ignition A new ignition module / control unit module / control unit. is supplied with cover, grommet, ignition lead and spark plug boot. MS 661, MS 661 C-M...

  • Page 42: Ignition Module

    7.13 : Push the red and black wires into the guide (arrow) – the red wire The test refers only to a spark test, must be under the black wire. not to ignition timing. MS 661, MS 661 C-M...

  • Page 43: Spark Test

    – Before starting the test, install a new spark plug in the cylinder and tighten it down firmly. – To run diagnosis on MS 661, – Before starting the test, install a select "Other STIHL Products". new spark plug in the cylinder...

  • Page 44: Spark Plug Boot

    STIHL press fluid, lead. b 16 – Remove the ignition module / control unit, b 7.3 : Hold the ignition lead and leg spring together and push them into the spark plug boot. MS 661, MS 661 C-M...

  • Page 45: Flywheel

    – Before installing the ignition lead, pack the high voltage output with : Unscrew the flywheel nut (1). STIHL multipurpose grease b 16. Do not use either graphite grease or silicone insulating paste. MS 661, MS 661 C-M...

  • Page 46: Testing Wiring

    – If no fault can be found, check the spark plug boot are in order, check ignition system with the aid of the the short circuit wire. troubleshooting chart, b 7.13 – Remove the rewind starter, b 9.2 MS 661, MS 661 C-M...

  • Page 47: Testing Wiring Harness

    – Remove the contact spring and retainer, b 7.12 – Remove the tank housing, : Position the grommet (3) so that b 13.11.4 the contour (1) faces the insulation (2). MS 661, MS 661 C-M...
  • Page 48 : Slide the grommet (1) into screw (3) firmly. position sideways and push it home until it is properly seated in – Install the ignition module, b 7.3 the crankcase. – Reassemble all other parts in the reverse sequence. MS 661, MS 661 C-M...

  • Page 49: Short Circuit Wire / With M-Tronic Removing And Installing

    – Remove the carburetor, b 13.4 (arrow) and pull off grommet (2) in direction of ring terminals. – Remove the tank housing, b 13.11.4 – Check the wiring harness and replace if necessary. MS 661, MS 661 C-M...
  • Page 50 (cylinder side) and into the carburetor box : Place the grommet (2) in position, locate its groove and slide it in sideways until the lug engages at the other side. MS 661, MS 661 C-M...

  • Page 51: Short Circuit Wire / With M-Tronic And

    – Remove the shroud, b 6.4 – Remove the rewind starter, b 9.2 – Remove the control unit, b 7.2 – Use STIHL press fluid to make The grommet (1) must be properly installation easier, b 16 seated in the opening.

  • Page 52: Heating

    (2) and already fitted. pull it out of the guides (arrows). : Press lug (arrow) on grommet (1) in direction of cylinder and push it out sideways. MS 661, MS 661 C-M...

  • Page 53: Installing

    (cylinder side) and into the carburetor box. : Place the grommet (3) in position, locate its groove and slide it in sideways until the lug engages at the other side. MS 661, MS 661 C-M...
  • Page 54 : Position cable lug (1) with its – Use STIHL press fluid to make : Position cable lug of ground crimped side facing outwards installation easier, b 16 wire (1) so that the crimped side and push the M-Tronic's red...

  • Page 55: Contact Spring

    (1) part way, disconnect the throttle rod (2) from the carburetor (1) at the same time. : Turn the ring terminal (1) up and pull it off the pivot pin on the retainer (2). MS 661, MS 661 C-M...
  • Page 56 (3) – take care not to overstretch the contact spring. : Use STIHL press fluid to ease installation – do not lubricate : Push the short circuit wire (4) grommet (1) with grease, b 16 through the ring (5).

  • Page 57: Ignition System

    (4) behind lever (5) on choke shaft at the same time. Short circuit wire (1) and ground wire (2) must be properly located in the guides (3, 4) – the loops (arrows) allow for movement. MS 661, MS 661 C-M...
  • Page 58 – If necessary, install new spark plug boot and/ or leg spring, b 7.6 Test ignition system: with ZAT 3 or ZAT 4 (use ZAT 3 as main spark gap see TI 32.94), b 7.5 MS 661, MS 661 C-M...
  • Page 59 – Resistance: spark plug boot to ground: spec. 1.5 – 12 kΩ – Check resistance of ignition lead (spark plug boot and control unit removed) Spec.: spec.< 10 Ω, If necessary, install new spark plug boot and/or control unit, b 7.6 MS 661, MS 661 C-M...
  • Page 60 7.2 Engine runs? Machine runs trouble-free, – Look for fault in fuel system or no further action necessary carburetor. – Check engine for leaks. – Check position of flywheel on crankshaft, b 3.6, b 6.2 MS 661, MS 661 C-M...

  • Page 61: M-Tronic

    It adjusts ignition timing and meters the exact quantity of fuel as a function of external conditions. It is no longer necessary to carry out a basic or standard carburetor setting. MS 661, MS 661 C-M...

  • Page 62: Testing

    Testing with Depending on the production date STIHL MDG 1 of the STIHL MDG 1 and the power tool to be tested, it is possible that the database may not up to date for Always perform tests with the the power tool concerned. In such a STIHL MDG 1 engine analyzer.

  • Page 63: Connecting Test Cables

    (arrow), disconnect and the screw connections, switch check contacts, b 8.3.3 contact and wiring harness between the control unit and solenoid valve. The STIHL MDG 1 must be installed between the spark plug boot and spark plug. MS 661, MS 661 C-M...

  • Page 64: Checking The Solenoid Valve

    8.5 socket, or check for lack of contact due to damaged insulation, replace solenoid valve if necessary, b 8.6 Connector (1) must be properly seated in solenoid valve. MS 661, MS 661 C-M...

  • Page 65: Checking Detection Of Start Conditions

    "ground" socket and red plug (2) connector. to "Volt" / "Ohm" socket. – Set multimeter to "diode test". : Test diode on switch unit (3) (microswitch) – follow instructions supplied with multimeter. MS 661, MS 661 C-M...

  • Page 66: Testing The Wiring

    (1) with red wire and test cable's black plug (2). : Measure resistance between terminal socket (1) with black Specified value: < 10 Ω. wire and screw (2) on control unit. Specified value: < 10 Ω. MS 661, MS 661 C-M...

  • Page 67: Wiring Harness

    Tronic / Heating, Removing and : Take out the screws (1) and Specified value: < 10 Ω Installing, b 7.10. remove the switch unit (2). : Check lever on choke shaft (3), replace if necessary, b 13.5.7 MS 661, MS 661 C-M...
  • Page 68 13.4 necessary and then test it, b 8.3.4 – Reassemble all other parts in the reverse sequence. : Position the switch unit (3) so that the solenoid valve (1) engages the recess (arrow). MS 661, MS 661 C-M...

  • Page 69: Solenoid Valve

    (2), then push it carefully into the mounting bore. Do not rotate the solenoid valve during this process – its sealing face must not be damaged. The solenoid valve (1) must be pushed squarely into the mounting bore. MS 661, MS 661 C-M...

  • Page 70: Troubleshooting Chart

    M-Tronic Troubleshooting Chart 8.7.1 Circuit Diagram 1 Stop switch 2 Choke switch 3 Diagnostic socket 4 Switch unit (choke module) 5 Solenoid valve (in carburetor) 6 Spark plug 7 Ignition lead 8 Control unit MS 661, MS 661 C-M...

  • Page 71: Engine Does Not Start

    Specified values – Install new carburetor, – Check the solenoid valve, obtained? b 8.3.4 b 13.4 b 8.3.4 – Look for fault in fuel system, check engine for leaks, b 13.11, b 13.5, b 6.2 MS 661, MS 661 C-M...

  • Page 72: In Position

    8.3.5 screw connections, b 8.3.5, b 8.3.6 b 8.3.5, b 8.3.6, b 8.3.3 – Look for fault in fuel system (inlet needle, lever, spring, diaphragm), Check engine for leaks, b 13.5, b 6.2 MS 661, MS 661 C-M...

  • Page 73: Engine Speed Drops Under Load - Engine Down On Power

    – Check the air filter and clean or replace if necessary, b 13.1 – Calibrate the control unit, Power tool in order? – Look for fault in fuel Troubleshooting completed system, check engine for leaks, b 13.5, b 6.2 MS 661, MS 661 C-M...

  • Page 74: Ignition - No Spark

    – Set correct air gap, b 7.3 – Check the air gap in order? between the control unit and flywheel, b 7.3 – Check ignition system with aid of Ignition System Troubleshooting Chart, b 7.13 MS 661, MS 661 C-M...

  • Page 75: Engine Stops Suddenly

    8.3.6, b 8.3.3 b 8.3.6, b 8.5, b 7.10 – Install new carburetor, Specified values – Check the solenoid valve, b 13.4 obtained?, b 8.3.4 b 8.3.4 – Check engine for leaks, b 6.2 MS 661, MS 661 C-M...

  • Page 76: Cut-Off Engine Speed Is Not Reached

    – Replace switch unit, wires, plug and screw obtained?, b 8.3.6 b 8.5 connections, b 8.3.5, b 8.3.3 – Look for fault in fuel system, check engine for leaks, b 13.11, b 13.5, b 6.2 MS 661, MS 661 C-M...

  • Page 77: Rewind Starter

    – the pawls move – Clean all components. outwards. – Reassemble all other parts in the reverse sequence. : Carefully ease the spring clip (1) off the starter post. – Pull the pawls out of the rotor. MS 661, MS 661 C-M...

  • Page 78: Rope Rotor

    – Remove the pawls, b 9.3 : Fit the rope rotor on the starter post so that the inner spring loop (arrow) engages the recess (1). – Fit the cover washer. MS 661, MS 661 C-M...

  • Page 79: Tensioning The Rewind Spring

    The starter grip must sit firmly in the rope guide bushing. : Thread the starter rope (1) If it droops to one side: Tension the through the opening (arrow) in rewind spring by one additional turn. the rope rotor. MS 661, MS 661 C-M...

  • Page 80: Segment

    – Reassemble all other parts in the reverse sequence. : Lift the segment (1) at the recess (arrow) and tab (2) until the pegs (3) are clear of the holes. – Inspect the segment, replace if necessary MS 661, MS 661 C-M...

  • Page 81: Av Elements

    – Inspect the spring with plug, annular buffer and handlebar holder, replace if necessary. : Take out the screw (1). – Use STIHL press fluid to make installation easier, b 16 : Push the stop buffer (1), taper first, into the bore until its groove (arrow) engages the housing rib (2).

  • Page 82: Fuel Tank

    Installing 10.3 AV Element on Fuel Tank : Push pegs (arrows) into handlebar (1) and fit handlebar – Use STIHL press fluid to make holder (2) in position. : Remove screw (1) from installation easier, b 16 handlebar. : Push the annular buffer (1) onto the handlebar holder (2) as far as stop –...
  • Page 83 (1) on the underside of groove (arrow). the machine. – Preassemble the plug, spring : Insert and tighten down the and retainer. screws (4) firmly. – Push the tank housing down a little and hold it there. MS 661, MS 661 C-M...

  • Page 84: Av Element On Handlebar

    Installing Installing : Fit bearing plug (1) in position. : Position the AV element (1) on – Use STIHL press fluid to make : Coat the screw (2) with the handlebar and cylinder. installation easier, b 16 threadlocking adhesive, fit it and...
  • Page 85 (arrow) so that the peg (2) : Remove the handlebar (3), check engages the seat in the it and replace if necessary. crankcase. – Inspect handlebar holder with AV spring and annular buffer, replace if necessary, b 10.4 MS 661, MS 661 C-M...

  • Page 86: Handlebar / Wrap Around Handlebar With Heating

    : Take out the screw (1). : Pull the wire (2) out of the guide : Ease the handlebar (3) sideways (arrow). and take it out of the guide. : Take out the screws (1) and remove the cover (2). MS 661, MS 661 C-M...
  • Page 87 (2) is pushed off in the process. – Insert the screws and tighten them down firmly. : Pull out the handlebar stiffener (3). – Check handlebar heating and replace handlebar if necessary, b 14.6 MS 661, MS 661 C-M...
  • Page 88 : Place wire (2) with pin and socket connector in position and push it into the guides (arrows) – the thin black wire to the generator and the thick black wire to the heater switch must be below wire (2). MS 661, MS 661 C-M...

  • Page 89: Control Levers

    : Pull the short circuit wire (1) out guides (arrows) – the short circuit of the guides (arrows) and push wire (3) must be a snug fit on the the ring terminal (2) out switch shaft (4). sideways. MS 661, MS 661 C-M...
  • Page 90 (1) must touch the contact spring (arrow) in position "0". – Reassemble all other parts in the reverse sequence. : Short circuit wire (1) must be seated in the guide (2) – loop (arrow) allows for movement. MS 661, MS 661 C-M...

  • Page 91: Throttle Trigger

    (2) and throttle trigger (3) – note installed position (arrow). : Disconnect the throttle rod (1) from the throttle trigger (2). : Attach the torsion spring (1) to the trigger (2) – note the installed position (arrow). MS 661, MS 661 C-M...

  • Page 92: Throttle Rod

    : Lift locking tabs (arrows) and pull – Remove the filter base, b 13.3 the retainer (1) out part way. – On versions without M-Tronic, : Disconnect the throttle rod (2) remove the choke rod, b 11.3.1 from the lever (3). MS 661, MS 661 C-M...
  • Page 93 (4, 5, 6), push them into the guides if necessary – loops (arrows) allow : Use STIHL press fluid to ease for movement. installation – do not lubricate grommet (2) with grease, b 16...

  • Page 94: Choke Rod Models Without M-Tronic

    – Inspect the choke rod and replace if necessary. – Reassemble all other parts in the reverse sequence. : Attach the throttle rod (1) to the trigger (2). MS 661, MS 661 C-M...

  • Page 95: Chain Lubrication

    : Remove the washer (1). – Reassemble in the reverse sequence. – Coat groove in fuel suction hose with STIHL press fluid, b 16 : Push the oil suction hose (1), pickup body first, through the housing bore (arrow). MS 661, MS 661 C-M...
  • Page 96 STIHL press fluid, b 16 Installed position is correct when "TOP" (arrow) faces outwards. – Reassemble all other parts in the reverse sequence. : Remove the sealing ring (1). – Check the oil pump and replace it if necessary MS 661, MS 661 C-M...

  • Page 97: 12.3.1 Adjusting Uprated

    (recessed in the housing), the bore (arrow). adjusting screw can be set to maximum oil flow. – Use a 6 mm drift to carefully drive in the new valve from outside – note installed depth. MS 661, MS 661 C-M...

  • Page 98: Fuel System

    – Remove the air filter, b 13.1 : Set the switch lever (1) to cold start. – Use STIHL press fluid to make installation easier, b 16 : Fit filter base (2) over the studs (arrows) and push it home until it is seated in the carburetor's sleeve.

  • Page 99: Carburetor

    (2) and put it to one side. : Disconnect spade terminal (1) : Disconnect impulse hose (1). from the contact spring (2) and pull the M-Tronic's black wire (2) out of the guides (arrows). MS 661, MS 661 C-M...
  • Page 100 Models with M-Tronic : Remove the carburetor (1). – Use STIHL press fluid to make installation easier, b 16 : Fit the carburetor (1) over the – Check the carburetor and service studs (arrows) so that the or replace it if necessary.
  • Page 101 (arrow). Versions with carburetor heating : Insert and tighten down the screw (2) firmly. – Use STIHL press fluid to make Models without M-Tronic: installation easier, b 16 : Hold the grommet (1) so that the frame (2) and the peg (4) match the openings (arrows) in the tank housing.

  • Page 102: 13.4.1 Leakage Test

    – Only remove the choke shaft, hose off the carburetor. throttle shaft and throttle shutter if they are stiff, clean the shaft and – Install the carburetor, b 13.4 bearing bore. – Reassemble all other parts in the reverse sequence. MS 661, MS 661 C-M...

  • Page 103: Carburetor

    – Check the sleeve, remove and signs of fatigue, i.e. the diaphragm replace it if necessary. distorts and swells and has to be replaced. – Check the metering diaphragm for signs of damage and wear. Install a new gasket. MS 661, MS 661 C-M...

  • Page 104: Inlet Needle

    : Take the inlet control lever (2) with spindle out of the inlet : Fit the inlet needle (1). needle’s groove. : Fit the spring (2) in the bore. The small spring under the inlet control lever may pop out. MS 661, MS 661 C-M...

  • Page 105: 13.5.5 Pump Diaphragm

    – Check the pump diaphragm for signs of damage and wear. Install a new gasket. MS 661, MS 661 C-M...

  • Page 106: 13.5.6 Lever On Throttle Shaft

    – Remove the carburetor, b 13.4 : Align the end cover (1) so that the : Push the wire (1) into the guides stub (2) faces the throttle shutter. (arrows). – Carburetor troubleshooting, b 3.6 MS 661, MS 661 C-M...

  • Page 107: Lever On

    13.5.7 Lever on Choke Shaft – Remove the carburetor, b 13.4 – Carburetor troubleshooting, b 3.6 : Fit the torsion spring (1) so that its leg (arrow) rests against the rib on the carburetor. MS 661, MS 661 C-M...

  • Page 108: Adjusting The Carburetor, Models With M-Tronic

    3.6 : Move the choke shaft in direction of cold start }, the lever (1) must operate the microswitch (arrow) – with an audible click. – Reassemble all other parts in the reverse sequence. MS 661, MS 661 C-M...
  • Page 109 : Screw down the high speed – Remove the low speed – the high speed screw (H) may screw (H) as far as stop. screw (L). otherwise be damaged. – Continue with "Pre-installing limiter cap". MS 661, MS 661 C-M...

  • Page 110: Adjusting The Carburetor

    (H) and low speed screw (L). Adjust engine speeds with tachometer or STIHL MDG 1 engine For the sake of clarity the adjusting analyzer (select "Other STIHL Products" / "Tachometer"). Adjust screws are shown on the exposed...

  • Page 111: 13.8.3 Standard Setting

    This completes the basic setting of the high speed screw (H) and the low speed screw (L). Version without limiter caps: The high speed screw (H) and the low speed screw (L) are now set. MS 661, MS 661 C-M...

  • Page 112: Manifold

    Turn the adjusting screws only very slightly. Even minor adjustments can noticeably affect engine running behavior. : Loosen the screw (1) and slip the hose clamp over the manifold (2) in the direction of the tank housing. MS 661, MS 661 C-M...

  • Page 113: 13.9.1 Impulse Hose

    (2) (about 15 cm properly seated. long) around the flange and pass the ends of the string through the intake opening. MS 661, MS 661 C-M...

  • Page 114: Tank Vent

    – Remove the retainer with switch shaft and put it to one side, b 11.1.1 : Pry the tank vent (1) out of its seat using the rib (2) for leverage. – Always install a new tank vent. MS 661, MS 661 C-M...

  • Page 115: Fuel Intake

    – Reassemble all other parts in the reverse sequence. : Use hook 5910 893 8800 to remove the pickup body (1) from the fuel tank. – Use STIHL press fluid to make 13.11 Fuel Intake installation easier, b 16 13.11.1 Pickup Body Do not overstretch the fuel hose.

  • Page 116: Fuel Suction Hose On Carburetor

    13.11.3 Fuel Suction Hose on Carburetor – Remove the carburetor, b 13.4 – Use STIHL press fluid to make : Remove screw (1) from AV installation easier, b 16 element on handlebar. : Fit fuel hose (1) with elbow connector (2) on the nipple (3) so...
  • Page 117 : Pull the tank housing (1) out of heating, b 7.10 : Check the stop buffer (1) at the the crankcase (2). ignition side and replace if necessary, b 10.4.1 – Inspect the tank housing and replace if necessary. MS 661, MS 661 C-M...
  • Page 118 – Pull the manifold into the tank reverse sequence. housing, b 13.9 : Lift the tank housing (1) until holes (arrow) in AV spring (2) line : Insert and tighten down the screw (3) firmly. MS 661, MS 661 C-M...

  • Page 119: Heating System

    "Ω". the connector tag (arrow). : Pull the wire (1) out of the guides and disconnect the flag terminal (2). : Take the heating element (3) off the studs. MS 661, MS 661 C-M...

  • Page 120: 14.1.3 Thermostatic Switch

    Check operation of thermostatic switch with the aid of the "Troubleshooting Chart", b 14.2. – Remove the carburetor, b 13.4 : Push the wire (1) into the guides (arrows). MS 661, MS 661 C-M...

  • Page 121: Carburetor Heating System Troubleshooting Chart

    Replace thermostatic switch, b 14.1.3 Carburetor heating element in order Circuit Diagram G = Generator 1 = Rear handle 2 = Handlebar 3 = Heater switch 4 = Thermostatic switch 5 = Heating element (carburetor) MS 661, MS 661 C-M...

  • Page 122: Handle And Carburetor Heating System

    If the system is in order, the ohmmeter will indicate a value of about 10 Ω in measuring range "Ω". : Separate the pin and socket connector (1). MS 661, MS 661 C-M...

  • Page 123: Heater Switch

    : To ensure the switch position is correct, slide the heater switch (1) with multiple tab (2) into the tank housing bore so that the nib (3) engages the recess (arrow). MS 661, MS 661 C-M...

  • Page 124: Heating Element In Rear Handle

    If the heating element is not fitted perfectly flat, heat transfer to the handle will be interrupted and the element may fail as a result of overheating. : Test the heating element, replace it if necessary. MS 661, MS 661 C-M...

  • Page 125: Heating Element In Handlebar

    If the heating elements are in good and separate the pin and socket condition the ohmmeter will indicate connector. a value of about 6.4 Ω (measured value 6.0 – 8.0 Ω) in measuring range "Ω". MS 661, MS 661 C-M...
  • Page 126 The flywheel must not touch the damage, replace if necessary. generator wire – this could cause a break in power supply. – Reassemble all other parts in the reverse sequence. MS 661, MS 661 C-M...

  • Page 127: 14.7.1 Handle Heating And Generator Troubleshooting Chart

    Install new rear handle heating element b 14.5 Resistance of rear handle heating element about 1.6 Ω? Check generator Resistance between engine ground Replace and generator connection generator about 0.5 – 1 Ω? b 14.7 MS 661, MS 661 C-M...
  • Page 128 10.5.1 Check the heater switch Replace (contact sleeve against switch housing) heater switch Closed: about 0Ω? b 14.4 Open: Circuit interrupted, b 14.3 Reconnect connector to thermostatic switch, b 13.4 System in order MS 661, MS 661 C-M...

  • Page 129: 14.7.2 Test Connections And Test Values

    Break in wire, Install new heating element handlebar damaged Short circuit – Repair insulation damaged insulation Pull out wire for this purpose MS 661, MS 661 C-M...
  • Page 130 Short circuit – repair insulation damaged insulation Circuit Diagram G = Generator 1 = Rear handle 2 = Handlebar 3 = Heater switch 4 = Thermostatic switch 5 = Heating element (carburetor) MS 661, MS 661 C-M...

  • Page 131: Heating Element Connecting Wires

    (3) and handlebar guides (arrows) and push connecting wire (2) – push them insulating tube (2) in direction of firmly together. throttle trigger. : Push the insulating tube (1) over the pin and socket connector. MS 661, MS 661 C-M...

  • Page 132: Connecting Wire Between Rear Handle And Generator

    – Reassemble all other parts in the – Pull the insulating tube off the reverse sequence. connecting wire. : Pull connecting wire (1) with pi and socket connector out of the guides (arrows) and put it to one side. MS 661, MS 661 C-M...
  • Page 133 (2) – connecting wire to : Push the connecting wire (1), handlebar and must be hooked in connector (2) first, through the place and underneath the grommet (3) from inside. generator wire. MS 661, MS 661 C-M...
  • Page 134 : Push the wires into the guide between the rib and handle heating so that the connecting wire to the handlebar is underneath the generator connecting wire. – Reassemble all other parts in the reverse sequence. MS 661, MS 661 C-M...

  • Page 135: Special Servicing Tools

    1117 890 0900 Attaching springs Press arbor 1118 893 7200 Installing ball bearing (clutch side of crankcase) Press arbor 1120 893 7200 Installing ball bearing (ignition side of crankcase) Combination wrench 1129 890 3401 Spark plug MS 661, MS 661 C-M...
  • Page 136 5910 890 3001 Installing and tightening bar mounting stud Piston support 5910 893 5300 Supporting the piston Hook 5910 893 8800 Removing pickup body Installing tool 5910 893 9601 Removing and installing collar nut in sprocket cover MS 661, MS 661 C-M...

  • Page 137: Servicing Aids

    (Loctite 270) High-strength threadlocking 0786 111 2101 adhesive up to 250°C (Loctite 272) Standard commercial solvent- Cleaning sealing faces and carburetor, based degreasant containing no crankshaft stubs and flywheel taper chlorinated or halogenated hydrocarbons MS 661, MS 661 C-M...
  • Page 138 englisch / english 0455 758 0123. VA0.G13. Printed in Germany...

This manual is also suitable for:

Ms 661 c-m

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