This demonstration guide answers one field question about a bump mechanism that no longer indexes. Measurements come before parts, and the notes are not a generic equipment FAQ.
Diagnose before replacing parts
Start with index-spring inspection. That reading separates a bump mechanism that no longer indexes from adjacent faults that share the same complaint.
If the measurement is out of spec, treat the bump-feed spring as the primary path. If it is in spec, do not replace the bump-feed spring just to complete a parts list.
Repair the failed system
The usual correction is the bump-feed spring, installed to the documented spec for this complaint.
A demonstration shop records the finding so the next technician is not repeating a guess about a bump mechanism that no longer indexes.
Stop before you make it worse
Do not converting to a metal blade on a head not rated for it. That shortcut hides the original measurement and creates a second failure.
If the machine still fails after the bump-feed spring is corrected, convert the visit to a broader diagnosis rather than stacking parts.
Written and published by Ridgeline Small Engine.