Installing Pistons

→ Absolute cleanliness is essential when working on the engine.

→ Lay removed engine parts on a clean base and make sure to cover them.

→ Use the cover for dust protection when fitting the engine NR.165  on the engine assembly support.

Installation for cylinder bank 1-3: 

Information 

• Observe installation sequence. 
• The central pistons of cylinders 2 and 5 are fitted onto the connecting rod without a cylinder sleeve. 
• The pistons for the outer cylinders 1, 3, 4 and 6 are preassembled in the cylinder housing. 

1. Fit individual pistons.
   1. 1.1. Align the gaps of the piston rings offset by 120° with respect to the middle piston ring (gap at the straight pin).

   Information 

   Pay close attention to the oil scraper rings when tightening the restraining strap.

2. Coat pistons generously with new engine oil. Fit commercially available restraining strap. Restraining strap 9659  must be fitted at the piston (piston junk).
   Fig 1: Identifying Piston Restraining Strap With Assembly Aid 9659/9

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3. Align restraining strap. The restraining strap lock should be aligned between the inlet valve recesses.
   Fig 2: Aligning Restraining Strap To Piston Rings

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   Information 

   • The assembly sleeve is used to position the restraining strap. 
   • Work quickly when positioning the strap so that the piston rings are not damaged. 
4. Insert the piston inverted into the assembly aid 9657  . Quickly press the piston downwards and press the restraining strap downwards at the same time with your other hand.
   Fig 3: Identifying Piston In Assembly Sleeve

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5. Slide hose pieces or aluminum sleeves over the threaded bolts to protect the pistons and piston rings.
6. Turn crankshaft pulley clockwise until the connecting rods of cylinders 2 and 5 are positioned at top dead center.
   NOTE: Loose parts in crankcase

   • Risk of engine damage

   → Cover crankcase bores with a clean cloth.

   Information 

   • It is advisable to get a second person to assist in fitting the circlip on the piston. 
   • Check that the piston-pin circlips are seated correctly. 
7. Fit pistons 2 and 5 on the connecting rod. Check installation direction.
   1. 7.1. Piston must be fitted so that the engraved arrow marking is always pointing towards the flywheel and the large valve recesses are on the intake side.
      Fig 4: Identifying Piston Installation Marking

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   2. 7.2. Cover crankcase bores with a clean cloth.
   3. 7.3. Coat piston pin with fresh engine oil and slide it in as far as it will go.
      Fig 5: Installing Piston Pins To Middle Pistons

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8. Fit piston-pin circlip -1-  on the piston by hand.
   Fig 6: Fitting Circlip On Piston

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9. Fit circlip by pressing it with a slotted screwdriver (approx. 5 mm wide) while at the same time sliding it towards the hook groove -arrow-  until it engages in the ring groove. Check again that the circlip is seated correctly.
   Fig 7: Fitting Piston-Pin Circlip

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   Fig 8: Locating Piston-Pin Circlip Installation Position

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10. Turn the crankshaft at the pulley so that the middle piston is flush with the sealing edge of the crankcase bore.
11. Prepare the cylinder housing, outer cylinder sleeves and pistons for installation.
12. Insert new O-rings into the cylinders. Coat the O-ring area with a generous amount of special grease (Part No. 000.043.205.10).
    Fig 9: Locating O-Rings Into Cylinder Housing

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13. Fit new O-rings onto the cylinder sleeves. Coat the O-ring area with a generous amount of special grease (Part No. 000.043.205.10).
    Fig 10: Greasing O-Rings On Cylinder Sleeve

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14. Fit outer cylinder sleeves in the cylinders. Align the cylinder sleeves in the cylinder. The flattened areas must face towards the other cylinder sleeves in the longitudinal direction.
    Fig 11: Locating Cylinder Sleeves In Cylinder Housing

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15. The recesses on the cylinder sleeve must align with the bores of the studs.
    Fig 12: Locating Cylinder Sleeve Installation Position

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16. Fit the outer cylinder sleeves using the pushing device 9660  .
    Fig 13: Identifying Pushing Device 9660

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    Fig 14: Fitting Outer Cylinder Sleeves Using Pushing Device

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17. The outer cylinder sleeves can also be pushed in using a hydraulic press.
    Fig 15: Pressing Cylinder Sleeve Using Hydraulic Press

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18. Oil the piston shank and fit a commercially available piston restraining strap. Slide the piston into the cylinder sleeve while pressing the piston restraining strap down at the same time.
    Fig 16: Fitting Outer Pistons In Cylinder Sleeve

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19. Check the position of the pistons. The engraved arrow  is pointing towards the flywheel side and the large valve recesses are on the intake side. Pull the piston far enough out again so that the piston pin can just be inserted.
    Fig 17: Identifying Piston Installation Marking

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    Fig 18: Identifying Outer Pistons Installation Position

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    Fig 19: Identifying Outer Pistons In Cylinder Housing

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20. Fit the piston pins into the associated pistons from the inside. The piston pin should only be inserted so far that the connecting rod can still be fitted.
    Fig 20: View Of Piston Pins On Outer Pistons

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21. Detach aluminum sleeves or hoses from the threaded bolts.
22. Fit cylinder base seal above the studs. The "TOP"  marking must be facing the observer.
23. Spacers 9651  must be placed on the outer studs.
    Fig 21: Locating Spacers 9651 On Outer Studs

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24. Slide preassembled cylinder housing onto the threaded bolt.
    Fig 22: Fitting Pre-Assembled Cylinder Housing

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    NOTE: Loose parts in crankcase

    • Risk of engine damage

    → Cover crankcase bores with a clean cloth.

25. Fit the piston pin and the piston-pin circlip for the outer pistons from the inside (through the middle cylinder bore).
    Fig 23: Installing Piston Pins To Outer Pistons

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26. Remove the cloth at the crankcase bores.
27. Once you have fitted the piston-pin circlips, slide the cylinder housing as far as the spacers 9651  and fix in place using two threaded sleeves from the special tool set of retaining nuts P140  .
28. Prepare middle cylinder sleeve. Fit new O-ring and apply a generous amount of special grease (Part No. 000.043.205.10).
    Fig 24: Greasing O-Rings On Cylinder Sleeve

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29. Position the cylinder sleeve on the studs. Pay attention to the flattened areas on the cylinder sleeve -arrows-  .
    Fig 25: Locating Middle Cylinder Sleeve

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30. Pushing device 9660  must be fitted on the stud. Lay a plastic washer on the cylinder sleeve and press the cylinder sleeve into place on the piston (piston junk) by turning the shifting wheel.
    Fig 26: Identifying Pushing Device 9660

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    Fig 27: Fitting Middle Cylinder Sleeve Using Pushing Device 9660

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31. Slowly turn the crankshaft clockwise at the pulley until the middle piston can no longer be seen in the gap between the cylinder housing and crankcase. Then press the cylinder sleeve into place with the pushing device until the restraining strap detaches from the piston shank.
32. Open the restraining strap lock using two screwdrivers and guide the restraining strap out between the crankcase and cylinder sleeve.
    Fig 28: Removing Piston Restraining Strap

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33. Then press in the middle cylinder sleeve as far as it will go using the handwheel.
    Fig 29: Fitting Middle Cylinder Sleeve

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34. Loosen the threaded sleeves (set of retaining nuts P140  ) on the studs until the spacers 9651  between the crankcase and cylinder housing can be removed.
35. Slide the cylinder housing towards the crankcase.
36. To prevent the cylinder housing from sliding out when you turn the crankshaft, secure the position using threaded sleeves from the set of retaining nuts P140  .
37. Complete the same steps for cylinder bank 1-3 to fit pistons for cylinder bank 4-6.
38. When the pistons have been completely fitted in both cylinder housings, turn the crankshaft twice in a clockwise direction at the pulley. The crank drive must not become jammed.