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Home›Repair guides›Cummins/Onan›Tappet (Valve Clearance) Adjustment

Cummins/Onan 6.5NH - 3CR / 6000 A — Tappet (Valve Clearance) Adjustment

Adjustments · Valve tappets

For the Cummins/Onan 6.5NH - 3CR / 6000 A, from the Cummins/Onan service manual.

Applies to: Cummins/Onan NH engine

Procedure

  1. Remove the valve covers.
  2. Crank the engine slowly by hand until the left hand intake valve (facing the flywheel) opens and closes.
  3. Continue about 1/4 turn until the flywheel mark and the gear cover TC mark are in line.
  4. Check that the gauge just passes between the valve stem and valve tappet; intake .003, exhaust .010.
  5. Turn the self-locking adjusting screw as needed to obtain the correct clearance.
  6. For the right hand cylinder, crank the engine one complete revolution, line up the marks again and repeat.

Tools required

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

Specs & values

  • Intake .003 inch
  • Exhaust .010 inch

Source: Cummins/Onan 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.

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