This demonstration guide answers one field question about rich mix or a failed crank seal that oils the muffler. Measurements come before parts, and the notes are not a generic equipment FAQ.
Diagnose before replacing parts
Start with muffler wetness and crank-seal leak-down. That reading separates rich mix or a failed crank seal that oils the muffler from adjacent faults that share the same complaint.
If the measurement is out of spec, treat the crank seals as the primary path. If it is in spec, do not replace the crank seals just to complete a parts list.
Repair the failed system
The usual correction is the crank seals, installed to the documented spec for this complaint.
A demonstration shop records the finding so the next technician is not repeating a guess about rich mix or a failed crank seal that oils the muffler.
Stop before you make it worse
Do not running a hotter plug to hide a rich condition. That shortcut hides the original measurement and creates a second failure.
If the machine still fails after the crank seals is corrected, convert the visit to a broader diagnosis rather than stacking parts.
Written and published by Ridgeline Small Engine.