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Discussion Starter · #1 ·
Gents:

Small but detailed question for the usual helpful crowd.

The exhaust header studs in my 1981 KZ550A2 have two different lengths of threaded section. One end of the stud is threaded for 11 mm along the stud while the other end is threaded for 15 mm.

Which end of the stud goes into the aluminum head, the longer 15 mm or the shorter 11 mm?

I tested one stud and the head will accept all of the 15 mm end, so the hole is at least that deep. Thanks guys. Don.
 

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From the schematic at babbits it appears the longer threaded end goes into the cylinder head. Number 5 on the picture.
 

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When the stud is properly installed, the exhaust clamp will not run out of threads before the nut gets tight. If it does,you run the risk of breaking the stud off.
 

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Discussion Starter · #4 ·
Kawpaul, Mike:

Thanks for your quick help with the Babbits fiche and the thread length rationale.

I have installed the studs with the 15 mm threaded section into the head. I wound them in until the last thread just disappeared. And the distance from the exhaust gasket seat to the tip of each stud is about 2.30 inches plus or minus 40 thou.

Interesting that the Kawasaki fiche is drawn with enough attention to detail that the length of threaded sections is revealled. Got to love those guys.
 

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When running in studs like this, sometimes double nutting helps in being able to turn it in tight. Tighten two nuts together and then drive with the top nut. If the threaded hole seems too tight, then I'd get the correct tap and carefully "Chase" or clean out the threads.
 

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Discussion Starter · #6 ·
Mike: MY old research department machinist told me that sometimes holes like these are purposely tapped with taper taps rather than bottoming taps. The ratonal is that the partially uncut threads in the bottom of the hole will act to stop and jam the stud just where it should be. So I didn't chase them. In my specific case the studs required a pretty good twist to insert them right from the beginning. So I guess that these holes were tapped with a slightly undersided tap, or the studs were slightly oversize. In other words, amazingly perfect........like the Japanese of the 1980s. Thanks.
 

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If you find those bolts/studs a bit too tight then a bit of oil on the threads will aid in running them in.
 

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Discussion Starter · #8 ·
Kawpaul:

I was going to put the copper based antisieze on them, which has oil, but I worried that the high temperatures would "coke" the oil and make them immovable in the future. So the holes were dry and the threads were dry.

Hopefully, I don't goof up this rebuild and have to find out if they are removable!!
 
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