Piston: Service and Repair

Remove/Install Pistons

Part 1:

Part 2:

Remove
1 Remove cylinder head
2 Remove oil pan
3 Remove oil pump
4 Remove oil deflector plate
- Engines with oil deflector plate

5 Unscrew conrod bearing cap (1)

CAUTION: Conrod (2) and conrod bearing cap (1) are marked together (arrow)

6 Lift conrod (2) up and out together with piston (4)

CAUTION: If the pistons are worn, the direction-of-travel arrows or colored dots stamped on the pistons are no longer visible, for this reason mark direction of travel on piston.

7 Use a screwdriver to press out piston pin retainer (5)

CAUTION: Do not damage piston. Use a clean cloth as a base.

8 Press out piston pin (6)
- If necessary, e.g. for repairing engine, Repairing conrod

9 Check side clearance of piston rings

Install
10 Assign standard size piston to cylinder bore

NOTE: When installing new standard size pistons.

- Install new pistons into used engines only if the cylinder bore does not have any abnormal wear, is within the dimensional tolerances for cylinder shape and roundness and the honing is visible and undamaged, if necessary, Measure cylinder bores.


11 Oil piston pin (6) and conrod bush
12 Assemble piston (4) and conrod (2)

NOTE: Assemble piston and conrod so that the arrow or colored dot on piston crown is pointing in direction of travel.

- The marking and the retaining lugs in the conrod are located on the left (at the inlet side).
- The shoulder (4a) on one of the piston pin hubs must face away from the direction of travel.

13 Push in piston pin (6) by hand.
14 Insert piston pin retainer (5) into the groove (arrow) on the piston.
15 Oil cleaned cylinder bores, conrod bearing journals, conrod bearing shells and pistons (4)

CAUTION: Install conrod bearing shell with oil hole in the conrod (2), otherwise the conrod bush will not be lubricated.

16 Fit on tensioning strap (7) for piston rings and tension
17 Install piston (4) with arrow or colored dot facing in direction of travel

CAUTION: The shoulder (4a) on one of the piston pin hubs must point in the opposite direction.

18 Screw on conrod bearing cap (1)

CAUTION: Screw conrod bearing cap (1) and conrod (2) with the markings (arrows) pointing toward each other.

19 Rotate crankshaft and inspect for clearance
20 Measure piston projection

NOTE: If piston projection is not correct, determine cause and specify appropriate repair measure.

21 Install oil deflector plate
22 Install oil pump
23 Install oil pan
24 Install cylinder head.