For the manner in which men live is so different from the way in which they ought to live, that he who leaves the common course for that which he ought to follow will find that it leads him to ruin rather than safety.
-Machiavelli

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Saturday, May 24, 2014

There Are Some Repairs...

that you just don't want to do. Like fixing spark plug threads. It's one thing when an engine is apart. Replacing threads means making chips. Engines don't like chips.
So...here's how it's done when the engine is together. On my friends '69 HD Shovel Head.

The weapon. This tap does a couple of different jobs. The end will act as an insertion tool for the threaded insert, it has a ramped cutter, and the upper section will cut the threads for the insert.



You need something to keep the chips from falling into the cylinder. CV axle grease is great for this job. It is thick enough to stick to the tap, but not too thick to be cleaned off easily.


The tap must be coated in grease. The very beginning is very tricky. You need to get this thing as straight as possible. To compound the problem, you cannot just start running this thing in all willy-nilly. You can only go in a portion of a turn at a time, back it out, clean the flutes, regrease it, and go again. If you turn too far, you'll build up too much of a chip...and that chip runs the risk of falling down. In other words, it's going to take a while.

Cotton swabs and grease are cheaper than engines. Take your time, keep it clean. I hate when my feet get in the shot, they're exhibitionist like that. I'm too lazy to edit a picture this morning.
The stressful part is over.

Install the appropriate length insert onto the tap. After you completely clean the tap, of course. It will be used as the insertion tool. Once the insert is in the head, you will use a special punch to swage the insert (I totally forgot to get a picture of that step, you'll just have to take my word for it).
BAM! The spark plug is back in.
This is a good job for an anti-social Friday evening. Pour a cocktail, crank up some tunes, and take it slow. Lucky for me, every Friday is an anti-social Friday.

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