Spark Plug Threads
RECONDITIONING SPARKPLUG THREADSNote
Reconditioning of sparkplug threads must be done with the cylinder head removed!
Remarks:
Denatured alcohol facilitates operations when working with aluminum.
Tapping thread in sparkplug hole
Use combined tap 998 5823-5 and thread insert
P/N 948756-2.
Note
Do not drill out sparkplug threads,
Combined tap
A: Thread section
B: Reamer section
C: Guide (old thread)
INSTALLATION OF THREAD INSERT
Because of restricted space, the retaining nut cannot be used on the installation tool. Instead the nozzle must be taped into position.
Note
For thread inserts that are finer than usual, it is extra important not to apply pressure to the tang when threading (both in the nozzle and the material).
Screw down the thread insert approx. 10 revolutions and check that the uppermost thread is at least 1/2 revolution in the bore and that no part of the insert is protruding from the bottom end of the bore.
If the insert has been screwed in too far, it must be turned until it is all the way through.
Break off the tang with a pair of flatnose pliers.
Test the reconditioned thread with a sparkplug. It should be possible to screw the sparkplug in easily by hand.