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Replacing the Ignition
How do I replace the ignition?
Today's small engines contain a solid-state ignition armature mounted adjacent to the flywheel. The only moving parts in the system are the magnets mounted in the flywheel, which interact with the armature to produce electrical current. Most ignition armatures are designed to be replaced, not repaired, if they fail. If yours is one of the early solid-state ignition armatures (manufactured by Briggs & Stratton through 1982), it may have replaceable parts. But you'll probably find that replacing the armature is the easiest solution if it fails. A great source of information regarding ignition testing can be found on our Ignition System Theory and Testing FAQ.
Most engines built through the early 1980s contain a set of mechanical points, known as breaker points, under the flywheel. The points open and close an electrical circuit required for ignition. You can improve the reliability of such an engine, if it's a Briggs & Stratton, by bypassing the breaker points system using a solid-state ignition retrofit kit. It's an easy modification.
Before you replace a suspect ignition armature, always test ignition with a spark tester (see "Servicing Spark Plugs"). Check for faulty electrical switches that could be the source of the problem (see "Braking System").
Many engine performance problems can be linked to maintenance issues such as stale fuel, dirty air filter, fouled spark plug, and deteriorated oil.
A great way to help avoid these problems would be to perform an annual tune-up using a Briggs & Stratton engine Maintenance Kit.
Installing And Adjusting A New Ignition Armature
An ignition armature
Ignition Armature must be set at a precise distance from the flywheel. Ask your Briggs & Stratton Authorized Dealer or consult our Engine Check Chart (PDF) for the proper gap for your engine. Common armature gap ranges are .006 - .010" and .010 - .014". Armatures are often packaged with a shim to assist in setting the gap. Microfiche or index cards of the proper thickness also work well.
Remove the old ignition armature mounting screws (image A)
Image A. Then, disconnect the stop switch wire from the flywheel brake and remove the armature.
Attach a replacement armature from the original engine manufacturer, using mounting screws (image A)
Image A. Then, push the armature away from the flywheel and tighten one screw (image B)
Turn the flywheel so the magnets are on the opposite side from the ignition armature (image C)
Place the appropriate shim between the rim of the flywheel and the ignition armature. While holding the shim, turn the flywheel until the magnets are directly adjacent to the armature (image D)
Loosen the tight screw so the magnets pull the ignition armature against the flywheel and shim. Then, tighten both mounting screws and rotate the flywheel until the shim slips free.
Testing A Stop Switch
Insert the spark plug lead on one end of a spark tester
Spark Tester (service part number 19368) and attach the tester's alligator clip to ground, such as an engine bolt (image E)
Place the equipment stop switch control in the OFF or STOP position. If the engine is not connected to the equipment, ground the stop switch wire to the cylinder. Attempt to start the engine using the rewind cord or key (if equipped), There should be no spark. If a spark appears, inspect the stop switch for damage. Consult your authorized service dealer if you find a faulty switch.
Place the stop switch control in RUN or START position. If the engine is not connected to the equipment, make sure the stop switch wire is not grounded. Attempt to start the engine. A spark should be visible in the tester. If no spark appears, check for broken wires, shorts, grounds or a defective stop switch.
Once you have confirmed that the stop switch is working, reconnect the spark plug lead.
Retrofitting An Older Ignition Armature
Breaker point ignition systems were common through 1982. You can improve ignition reliability on a single-cylinder Briggs & Stratton engine equipped with breaker points and a two-leg armature by installing a solid-state ignition conversion kit
Ignition Conversion Kit (service part number 394970) that bypasses the points (ignition conversion kit will not work with a three-legged ignition armature
Three-Legged Ignition Armature). For additional installation procedures, please download our Magnetron Retro-Fit Installation Instructions (PDF). Consult a Briggs & Stratton Authorized Dealer for the proper conversion kit.
Disconnect the spark plug lead and secure it away from the plug. Then, remove the flywheel and discard the old flywheel key.
Cut the armature primary and stop switch wires as close as possible to the dust cover (image A)
Image A. Then, remove the dust cover, points and plunger, and plug the plunger hole with the plug supplied in the conversion kit.
Loosen the screws and remove the armature. Then, cut the armature's primary wire to a 3" length (image B)
Image B. Strip away 5/8" of the outer insulation. Then, use a utility knife or razor blade to scrape off thoroughly the red varnish insulation underneath. Take care not to nick or cut the wire (image C)
Install the conversion module (image D)
Image D. Modify the air vane brackets or guide for clearance, as required.
Fasten a pin punch in a bench vise. Push open the spring-loaded wire retainer by pressing down on the punch. With the slot open, insert the armature's primary wire and a new stop switch wire (if required), together with the module primary wire (image E)
Image E. Then, release the wire retainer, locking the wires in place. Secure the wires by soldering the ends with 60/40 rosin core solder.
Twist the armature ground wire and module ground wire together (two turns) close to the armature coil (image F)
Image F and solder the twisted section, taking care not to damage the armature coil casing. Avoid crossing these wires with those inserted in the wire retainer in Step 5.
Remove the shortest ground wire by cutting it off close to the soldered connection. Cement the wires to the armature coil, using a generous amount of silicon sealer to protect against vibrations.
Use a screw to attach the armature/module ground wire to the armature (image G)
Image G. Then, fasten the armature to the engine so that the wire retainer is toward the cylinder.
Remove the remainder of the original stop switch wire as close as possible to the terminal on the engine. Then, route the new wire from the module, following the same path as the original. Fasten the new wire in place. Make sure the wire does not interfere with the flywheel.
Install the flywheel, using the replacement flywheel key in your kit, and tighten the flywheel nut or rewind clutch (see "Inspecting the Flywheel & Key"). Set the armature air gap (see above "Installing and Adjusting a New Ignition Armature"). Then, test the stop switches (see above "Testing a Stop Switch").
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