# Crankshaft standard journal diameters and out-of-round (NA6)

Canonical URL: https://miatatorque.com/spec/crankshaft-standard-journal-diameters-na6/

Applicability: NA 1990–1993 (B6) — Other years inferred from 1990 factory evidence.

Confidence: fsm

Main journal
Diameter: 49.938–49.956 mm (1.9661–1.9668 in)
Out-of-round: 0.05 mm (0.0020 in) max.
Crankpin journal
Diameter: 44.940–44.956 mm (1.7693–1.7699 in)
Out-of-round: 0.05 mm (0.0020 in) max.

Always confirm against your factory manual. Match every restriction and follow all stages and procedure notes. Disputed claims must not be automatically resolved. The complete record below preserves every printed unit, source claim and procedure.

```json
{
  "id": "crankshaft-standard-journal-diameters-na6",
  "name": "Crankshaft standard journal diameters and out-of-round (NA6)",
  "aliases": [],
  "applies_to": [
    {
      "gen": "NA",
      "years": [
        1990,
        1993
      ],
      "engines": [
        "B6"
      ],
      "note": "Other years inferred from 1990 factory evidence."
    }
  ],
  "kind": "non-torque",
  "value_text": "Main journal\nDiameter: 49.938–49.956 mm (1.9661–1.9668 in)\nOut-of-round: 0.05 mm (0.0020 in) max.\nCrankpin journal\nDiameter: 44.940–44.956 mm (1.7693–1.7699 in)\nOut-of-round: 0.05 mm (0.0020 in) max.",
  "procedure": {
    "notes": "Measure each journal in X/Y directions at two points. These standard diameters do not specify the crank nose, pulley, keyway or crank-center-bolt torque. Preserve the fillet roll area when grinding."
  },
  "confidence": "fsm",
  "sources": [
    {
      "source": "fsm-1990",
      "page": "B–58 (PDF p. 85)",
      "as_printed": "Main journal\nDiameter: 49.938—49.956mm (1.9661—1.9668 in)\nOut-of-round: 0.05mm (0.0020 in) max.\nCrankpin journal\nDiameter: 44.940—44.956mm (1.7693—1.7699 in)\nOut-of-round: 0.05mm (0.0020 in) max.",
      "verified_years": [
        1990,
        1990
      ],
      "document": {
        "id": "fsm-1990",
        "tier": 1,
        "title": "1990 Mazda MX-5 Miata Workshop Manual",
        "part_number": "1193-10-89C",
        "covers": [
          {
            "gen": "NA",
            "years": [
              1990,
              1990
            ],
            "engines": [
              "B6"
            ]
          }
        ],
        "url": "https://archive.org/details/1990-mazda-mx-5-miata-workshop-manual_202411"
      }
    }
  ],
  "jobs": [],
  "system": "engine",
  "component": "inventory-pass-2026-10",
  "componentName": "Service measurements and fasteners",
  "sequence_diagrams": [],
  "url": "https://miatatorque.com/spec/crankshaft-standard-journal-diameters-na6/"
}
```