The Stihl MS 650 and MS 660 chainsaw service and repair Ignition System guide will help with the test and repair of the chainsaw. A Service Manual detailing the various troubleshoot faults and problems, as well as more complete chainsaw repair information, is available to download. Also a Stihl MS650 and MS660 Parts List, Operator Manual, and carburetor manual are also available to view or download as a PDF which can be read on any device or printed.

Ignition System 7.1 Ignition Module 7.2 Ignition Timing

Exercise extreme caution when troubleshooting or carrying out maintenance and repair work on the ignition system. The high voltages that occur can cause serious or even fatal accidents.

Troubleshooting on the ignition system should always begin at the spark plug – b 4.5

Ignition timing is fixed and cannot be adjusted during repair or servicing work

Since there is no mechanical wear in these systems, the ignition timing cannot get out of adjustment as a result of wear.

The ignition module accommodates all the components required to control ignition timing. There are two electrical connections on the coil body:

• • High voltage output (1) for ignition lead

• • Connector tag (2) for short circuit wire

Testing in the workshop is limited to a spark test.

A new ignition module must be installed if no ignition spark is obtained (after checking that wiring and stop switch are in good condition)

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The electronic (breakerless) ignition system basically consists of an ignition module (1) and flywheel (2).

Removing and Installing

• Remove the shroud – b 6.2

1

• Remove the fan housing with rewind starter – b 8.2

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• • If necessary, use a suitable punch to drive the pin out of the wire retainer (1).
• Remove the wire retainer.
• If necessary, install the ignition lead, b 7.2.3, before fitting the wire retainer.

• Coat threads of screws with Loctite 242, b 17, before installing.

Reassemble in the reverse sequence.

• • Secure ground wire (2) with screw (3).

• • Tighten down screws (3 + 4) moderately.
  • Connect the short circuit wire (5).
  • Position the ignition lead (1) in the guide (arrow).
    • Pull off the short circuit wire (1).
    • Take out the screw (2).
    • Remove the ground wire (3).
    • Take out the screw (4).

– Remove the ignition module.

If the ignition lead or spark plug boot is damaged, install new parts –

b 7.2.3.

• On machines with handle and/or carburetor heating, position the wire (1) under the ignition module.

1

2

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• Push the wire (2) into the wire retainer (arrow).
• Rotate the flywheel until the “N” mark (arrow) is in line with the top of the ignition module.

Testing the Ignition Module

• • Slide the setting gauge (1) 1111 890 6400 between the

arms of the ignition module and the flywheel.

• Press the ignition module (2) against the setting gauge.
  • Tighten down the screws (3) firmly – b 3.5
• Remove the setting gauge and use a feeler gauge to check the air gap. It should be 0.2 mm.
• Install the fan housing with rewind starter – b 8.2
• Fit the shroud – b 6.2

To test the ignition module, use either the ZAT 4 ignition system tester 5910 850 4503 or the ZAT 3 ignition system tester

5910 850 4520.

3

2

3

1

The ignition test refers only to a spark test, not to ignition timing.

Using the ZAT 4 ignition tester 5910 850 4503

– Before starting the test, install a new spark plug in the cylinder and tighten it down firmly –

b 3.5

● Crank the engine quickly with the rewind starter (min. 1,000 rpm) and check spark in the tester’s window (2).

Warning!

The engine may start and accelerate during the test.

If a spark is visible, the ignition system is in order. If no spark is visible in the window (2), check the ignition system with the aid of the troubleshooting chart – b 7.6

Using the ZAT 3 ignition tester 5910 850 4520

• Before starting the test, install a new spark plug in the cylinder and tighten it down firmly –

b 3.5

• • Remove the spark plug boot and connect it to the input terminal (1).
  • Push the tester’s output terminal (3) onto the spark plug.

– Set the Master Control lever to “#“

● Remove spark plug boot and connect it to the terminal (2).

● Attach ground terminal (1) to the spark plug.

● Use adjusting knob (3) to set the spark gap to about 2 mm.

Spark Plug Boot/

Ignition Lead

While using the ZAT 3, hold it only by the handle (4) or position it in a safe place. Keep fingers or other parts of your body at least 1 cm away from the spark window (3), high voltage connection (2), ground connection (5) and the ground terminal (1).

Warning!

High voltage – the risk of electric shock.

– Set the Master Control lever to “#“.

● Crank the engine quickly with the rewind starter (min. 1,000 rpm) and check sparkover in the tester’s window (3).

Warning!

The engine may start and accelerate during the test.

If a spark is visible, the ignition system is in order.

If no spark is visible in the window (3), check the ignition system with the aid of the troubleshooting chart – b 7.6.

• Remove the ignition module –

b 7.2.1

• Pull the grommet (1) off the high voltage output (2).
• Unscrew the ignition lead (3) from the contact pin and pull it out of the high voltage output.
• Remove the grommet and insulating tube (4) from the ignition lead.
• Pull the cover off the spark plug boot.

• Use suitable pliers to pull the leg spring out of the spark plug boot.
• Unhook the leg spring from the ignition lead.
• Pull the boot off the ignition lead.
• Cut new ignition lead to a length of 185 mm.
• Use a pointed tool to pierce the center of the ignition lead’s insulation, about 15 mm from the end of the lead.
• Pinch the hook of the leg spring into the center of the lead (arrow).

Flywheel

• • 1. Removing
• Coat inside of spark plug boot with Press Fluid OH 723.
• • Push the ignition lead and leg spring into the spark plug boot.

• • Make sure the leg spring locates properly inside the spark plug boot.
• Push the cover over the spark plug boot.
• Slip the insulating tube and grommet over the ignition lead.
• Pack the high voltage output with STIHL multipurpose grease – b 17

Do not use either graphite grease or silicone insulating paste.

• Screw the ignition lead into the ignition module.
• Push the grommet over the high voltage output.
• Install the ignition module –

b 7.2.1

• Remove the fan housing with rewind starter – b 8.2
• Use locking strip to block the piston – b 5.4
• Use socket 5910 893 5610 (for torque wrench) to unscrew the flywheel nut (arrow).

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• • Use a pointed tool to pierce the center of the other end of the ignition lead which screws into the module.

• • Back off the thrust bolt (1) of the puller (2) 1106 890 4501.

• • Screw puller into the flywheel (3).

Installing 7.4 Contact Spring

• • • Hold the puller steady and screw home the thrust bolt (1) until the flywheel is released.

– Remove the puller from the flywheel.

Degrease crankshaft stub, key, and slot in flywheel hub with standard solvent-based degreasant containing no chlorinated or halogenated hydrocarbons – b 17

• Check that key (arrow) is properly seated.
• Fit the flywheel in position.
• Fit and tighten down the flywheel nut firmly – b 3.5
• Set gap between ignition module and flywheel – b 7.2.1

Reassemble all other parts in the reverse sequence

• Remove the carburetor –

b 12.2.1

• Set the Master Control lever to CHOKE.
• Pull off the connector (arrow).
  • Pull off the flywheel.

Inspect flywheel and magnet poles for signs of damage or blue discoloration. If you find any damage, install a new flywheel.

• • Push the contact spring down and past the cam (1)

Stihl MS 650 and MS 660 chainsaw Ignition repair and fault finding.