Kohler PCH680 / PCH740 — Cylinder Leakdown Test (Dual Gauge)
Testing & diagnosis · Engine
For the Kohler PCH680 / PCH740, from the Kohler service manual.
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Procedure
- Run engine until oil temperature reaches and maintains 150°F (66°C) or more for a minimum of 5 minutes.
- Remove spark plug(s) and air filter.
- Rotate crankshaft until piston is at top dead center (TDC) of compression stroke. Hold engine in this position.
- Connect an air source (at least 100 PSI) to tool.
- Turn regulator knob clockwise. Confirm both gauges read approximately same air pressure from 0 to 80 PSI. Release pressure before proceeding.
- Install adapter hose into spark plug hole.
- Turn regulator knob clockwise until left gauge reads 20 PSI.
- Slowly turn regulator knob clockwise until left hand gauge maintains selected test pressure (80 PSI recommended for engines over 200 cc).
- Compare right gauge reading to Test Pressure Chart to identify percentage of leakage.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Left gauge 80 PSI recommended for engines over 200 cc
- Left gauge 35 PSI recommended for single cylinder walk-behind push mower applications
Source: Kohler service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.