This demonstration guide answers one field question about a valve that sticks open and kills compression. Measurements come before parts, and the notes are not a generic equipment FAQ.
Diagnose before replacing parts
Start with compression with the valve closed versus open. That reading separates a valve that sticks open and kills compression from adjacent faults that share the same complaint.
If the measurement is out of spec, treat the decompression valve as the primary path. If it is in spec, do not replace the decompression valve just to complete a parts list.
Repair the failed system
The usual correction is the decompression valve, 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 valve that sticks open and kills compression.
Stop before you make it worse
Do not holding the valve open while cutting. That shortcut hides the original measurement and creates a second failure.
If the machine still fails after the decompression valve is corrected, convert the visit to a broader diagnosis rather than stacking parts.
Written and published by Ridgeline Small Engine.