How to Fix the Magneto of a 4.5 MTD 22-Inch Yard Machine Lawn Mower

Turn off your Yard Machine mower and open its front hood to access the Briggs & Stratton engine.

Look back along the top of the engine block for the flywheel piece. This piece is distinctive due to its circular design and bolt-covered iron shroud. Remove the bolts from the shroud using a socket wrench, and then set the flywheel's shroud aside.

Note the incremental gap between the flywheel and the part directly in front of it. This part is the magneto, and the gap between it and the flywheel is the air gap. The magneto is a largely rectangular black part that is smaller than the flywheel and features an iron disc on its end. Measure the air gap using a caliper and ensure the gap is between 0.010 and 0.015 of an inch in width. If the air gap is even slightly misadjusted, the magneto can fail and the mower may not operate properly.

Adjust the flywheel's proximity to the magneto if the air gap's width falls outside of the required 0.010 to 0.015 specification by removing the bolt at the center of the flywheel to loosen its placement against the engine block. Press against the flywheel once this bolt is removed to incrementally move it closer or farther away to the magneto, as necessary.

Remeasure the air gap with the caliper to ensure it is correct then reinsert the single bolt directly into the center of the flywheel where it was previously removed.

Reattach the shroud to the flywheel with its bolts and your socket wrench.