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Home >> BMW >> 1971 >> 2800CS Not Available Trans >> Repair and Diagnosis >> Engine Mechanical >> Mechanical >> BMW Engines - 2500, 2800, 3.0 & BAVARIA 6 Cylinder >> Piston Pin Replacement

Piston Pin Replacement

  1. With piston and rod assembly removed, remove circlips from piston pin hole in piston. Drive out piston pin and separate piston from connecting rod. Thoroughly clean and inspect rod and piston.
  2. Piston pins are manufactured in two classes. Pin class is designated by color code on pin or a letter stamped in pin. A corresponding letter is stamped in piston. Pin-to-piston clearance is same for each class of pin, but pin-to-rod clearance varies depending on class of pin. See Specifications .
    PISTON PIN CLASS DESIGNATION

    Application Pin Diameter
    White, or "W" 8660-.8661" (21.997-22.000 mm)
    Black, or "S" 8659-.8660" (21.994-21.997 mm)
  3. Classes of pins and pistons must not be interchanged. If piston or pin is replaced, it must be replaced with one of a corresponding class and weight. Weight classification is designated by a "+" or a "-" stamped in top of piston.
  4. Check pin-to-piston clearance, if clearance exceeds that specified and pin is not worn, replace piston. Check pin-to-rod clearance, if clearance exceeds that specified, depending on pin class, new bushing must be installed.
  5. Press out old bushing and install new one with split in bushing rotated 90° from oil hole in connecting rod. Drill through oil hole in connecting rod. Ream bushing to specified clearance with piston pin.
  6. If connecting rod is replaced, replace with rod which is within 4 grams of rod being replaced. Position piston on connecting rod with arrow on piston facing in same direction as oil hole in connecting rod. Lubricate and install piston pin and circlips.
    Fig 1: Piston & Connecting Rod Assembly & Markings
    G09325561Courtesy of BMW OF NORTH AMERICA, INC.
CRANKSHAFT MAIN & CONNECTING ROD BEARINGS

Engine MAIN BEARINGS CONNECTING ROD BEARINGS
Journal Diam. In. (mm) Clearance In. (mm) Thrust Bearing Crankshaft End Play In. (mm) Journal Diam. In. (mm) Clearance In. (mm) Side Play In. (mm)
1969-73              
  Red Code 2.3614-2.3618 (59.98-59.99) .0012-.0028 (.030-.070) No. 4 .0033-.0069 (.085-.174) 1.8890-1.8894 (47.98-47.99) .0013-.0027 (.033-.069) .....
  Blue Code 2.3610-2.3614 (59.97-59.98) .0012-.0027 (.030-.068)