Repairing Spark Plug Threads

NOTE: the spark plug threads in the cylinder head can be repaired with the HELI-COIL Repair Set.

Repairing
1. Remove appropriate cylinder head cover. Service and Repair
2. Set piston at respective cylinder to 20° - 30° before TDC.





3. Pack grooves (arrows) of the combination thread tap (9) of the thread tapping unit with grease and screw combination thread tap into the damaged thread.
- When performing this step, push the guide bush (11) into the spark plug recess.

CAUTION: If cylinder head is installed, unscrew combination tap after approx. each five turns, clean grooves of chips and grease and re-pack with grease.





4. Check length of HELI-COIL threaded insert (8).
Use only the HELI-COIL insert with 10.2 mm block length.





5. Install HELI-COIL threaded insert.
To do this, place HELI-COIL insert (8) into the installation tool so that the tang (arrow) of the insert is facing the pretensioning cartridge (16).
Turn HELI-COIL insert with fitting spindle (13) through the pretensioning cartridge far enough for the tang (arrow) to be flush with the face end of the pretensioning cartridge.





- Fit installation tool onto the tapped hole, hold jacket sleeve (15) tight and turn insertion spindle until the stop ring (14) is resting against the jacket sleeve.

NOTE: When screwing in the HELI-COIL threaded insert, turn back jacket sleeve (15) slightly if it jams.





6. Break off tang (arrow) of HELI-COIL threaded insert.
- This is done by fitting sleeve (18) of tang breaking unit over the tang, introducing opened pliers (17) into the sleeve as far as the marking (arrow) and closing pliers.
The serrated lock (S) must engage.
- Turn sleeve (15) to the left as far as the stop and hold tight.
- Move pliers slightly up and down and break off tang.

CAUTION: If tang inadvertently drops onto piston crown, it must be removed with a magnet.

- Rotate crankshaft several times with starter and contact handle in order to remove any chips which may have dropped onto the piston crown.





7. Caulk HELI-COIL threaded insert.
- To do this, grease the tapered thread of the caulking tool (6), screw caulking tool into the installed HELI-COIL insert, tighten to 25 Nm and remove caulking tool.