Countersunk Threads

RECONDITIONING COUNTERSUNK THREADS

Cylinder head bolts and the crankshaft main bearing bolts have this type of thread. Remarks: Denatured alcohol facilitates operations when working with aluminum.

DRILLING




Measure the drill depth so the drill does not go to deep.

Drill out the hole using the specified drill (included in the kit or refer to table).

Blow hole clean and prevent metal chips entering the engine by covering over or by rinsing parts afterwards.

TAPPING NEW THREADS




Threading of the cylinder head bolt holes requires a longer thread pitch than normal (Thread tap: 951 2584).

On the crankshaft main bearing threads, one side has a countersunk hole that is so small it will also be threaded by the thread tap. This is OK.

Thread all holes until the tap touches the bottom. Blow clean to prevent metal chips or particles entering the engine.

INSTALLATION OF THREAD INSERT




To reach the threads with the thread insert disassemble the installation tool.

Using only the handle and spindle turn the insert down until the end of the insert is 1/2 revolution in the threaded section. Turn in stages, checking the depth.

Break off the tang with tang breaker.

Blow hole clean and check the tang has been removed. Test the reconditioned thread with a bolt It should be possible to screw the bolt to the bottom without using force.