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Yanmar 4TNE88 — Valve seat correction procedure

Repair & overhaul

For the Yanmar 4TNE88, from the Yanmar service manual.

Applies to: Yanmar 4TNE88, Yanmar TNE series engine

Before you start

  • Thoroughly remove valve compound or grindstone powder after correction.

Procedure

  1. When slightly worn, lap the seat surface with valve compound mixed with oil.
  2. When heavily worn, correct the seat surface using a seat grinder or seat cutter.
  3. Correct the roughened seat surface with a seat grinder or seat cutter (intake 30 deg, exhaust 45 deg).
  4. If seat width is enlarged, correct with a 70 deg grinder then grind to standard width with a 15 deg grinder.
  5. Knead valve compound with oil and finish the valve seat by lapping, finally lapping using only oil.

Tools required

Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.

Specs & values

  • Intake valve seat angle 30 deg / Exhaust 45 deg

Full service-parts list: Yanmar 4TNE88 →

Source: Yanmar 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.

More Yanmar repair guides →