Repairing Spark Plug Threads

NOTE: Numbers in parentheses ( ) indicate a component or tool in the associated illustration.

1. Remove cylinder head cover.
2. Position piston of cylinder to be repaired to 20 - 30° BTDC.
3. Pack with grease, the grooves (arrows) of Heli-Coil, or equivalent, combination thread tap (9) of thread tapping unit
4. Pull off stop ring (10).
5. Screw combination thread tap (9) into damaged thread.
6. Guide combination thread tap (9) with guide bush (11) pushed into spark plug recess.
7. Screw in combination thread tap (9) sufficiently until guide tube (12) touches and is resting against the groove (arrow) on the guide bush (11).

NOTE: With the cylinder head installed, unscrew combination thread tap (9) after each 5 revolutions, then clean grooves of metal particles and grease then re-pack with grease.

8. Check length of Heli-Coil, or equivalent, threaded insert (8).

NOTE: Use threaded insert (8) with 10.2 mm block length.





9. Insert threaded insert (8) into fitting tools so that the stud (arrow) of the insert (8) is facing the pre-tensioning cartridge (16).
10. Screw in threaded insert flush (arrow) into pre-tensioning cartridge (16) using the spindle (13).
11. Fit the fitting tool onto tapped hole.
12. Hold jacket sleeve (15) tight.
13. Turn screw-in spindle (13) sufficiently until the stop ring (14) is resting against the jacket sleeve (15).

NOTE: If jacket sleeve (15) jams tight when screwing in, turn back slightly.





14. Fit sleeve (18) over driving stud (arrow)
15. Fix driving stud (arrow) in place with pliers (17) (serrations).
16. Turn sleeve (18) to left as far as possible.
17. Move pliers (17) up and down slightly, break off driving stud (arrow).

NOTE: If driving stud drops onto the piston crown, it must be removed with a magnet.

18. Screw in degreased caulking tool (6) and tighten to 25 Nm.
19. Crank engine with starter to remove any metal particles which may have dropped onto the piston crown.