| Lawnmower Tune-Up |
| A minor tune-up gets a lawnmower started again. |
From "Trade School"
episode DTRS-210 |
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Dillon pulls and inspects the spark plug. To determine whether the plug needs to be released, he consults with Ed who inspects the center electrode (figure F). The electrode is still flat and hasn't been rounded off at the edges, so Ed suggests that rather than replacing the plug, a quick scrub on a wire wheel should suffice (figure G).
Before replacing the plug, Dillon also checks the spark plug gap. Specs for this mower state that the distance between the center electrode and ground wire should be 30/1000's of an inch. Using a gap gauge, Dillon confirms that the spark plug gap is correct (figure H).Having replaced the spark plug, Dillon uses a ratchet wrench to pull off the covers on the mower to expose the engine (figure I). His final adjustment is the armature air gap. The air gap is the distance between the rotating flywheel magnet and the ignition coil (figure J). Under normal operations, this powerful magnet spins near the coil creating an electro-magnetic charge that travels down the coil to the spark plug resulting in the all-important spark. If the gap is too large or too small, the engine will not work efficiently.
Dillon uses flat feeler gauges to determine that the armature air gap is too small on this mower. For this mower, manufacturer's specifications suggest it should at least be 12/100th's of an inch (figure K). He loosens the coil, pulls it back, and then places the feeler gauges of the correct size in between the coil and flywheel magnet (figure L). Dillon tightens the coil at his measurement, removes the gauges and replaces all the engine covers.The mover starts easily on the first pull (figure M); Dillon is ready for his next challenge.
In the next segment, Dillon revs up his education with a carburetor overhaul.
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