This demonstration guide answers one field question about rust that increases the magnetic gap. Measurements come before parts, and the notes are not a generic equipment FAQ.
Diagnose before replacing parts
Start with lamination rust map. That reading separates rust that increases the magnetic gap from adjacent faults that share the same complaint.
If the measurement is out of spec, treat the coil as the primary path. If it is in spec, do not replace the coil just to complete a parts list.
Repair the failed system
The usual correction is the coil, installed to the documented spec for this complaint.
A demonstration shop records the finding so the next technician is not repeating a guess about rust that increases the magnetic gap.
Stop before you make it worse
Do not wire-wheeling laminations down to a knife edge. That shortcut hides the original measurement and creates a second failure.
If the machine still fails after the coil is corrected, convert the visit to a broader diagnosis rather than stacking parts.
Written and published by Ridgeline Small Engine.