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