Kubota — Testing Engine Compression
Testing & diagnosis · Engine cylinders
From a Kubota service manual covering: Hurth HBW 100, Hurth HBW 125, Hurth HBW 150, Hurth HBW 250, Hurth HBW 35, Hurth HBW 50, M-25XPB, M-35B, M-40B. Check it applies to your exact model before use.
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Procedure
- Warm engine to normal operating temperature; verify oil level and air filter.
- Move the control lever to a position for shutting off the fuel.
- Remove all glow plugs and install compression gauge/adapter on one cylinder.
- Close the raw water seacock (thru-hull).
- Crank the engine and record the maximum gauge reading per cylinder.
- Compare cylinders; maximum difference must be 10% or less.
- Reinstall glow plugs with anti-seize, reset fuel shut-off, open seacock.
Tools required
- Compression gauge/adapter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Standard: 412 - 469 psi (2.84 - 3.24 MPa)
- Limit: 327 psi (2.26 MPa)
Source: Kubota 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.