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Author Topic: saving a 1980 KZ750 twin  (Read 56586 times)

Offline doc_rot

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Re: saving a 1980 KZ750 twin
« Reply #440 on: Jul 11, 2018, 00:11:30 »
Small update, but one of particular interest to kz750 twin owners.

I was cross referencing part numbers and realized the z1/kz1000 share the same head studs as the KZ750 twin. This means you can use APE's heavy duty head studs and nuts which are intended for the z1/KZ1000. I have bought a set and can now confirm, however, you do end up with 4 extra studs and nuts you don't need. These bikes are notorious for head gasket leaks, increased compression will likely make this worse, hopefully this will help address that.
« Last Edit: Jul 11, 2018, 00:16:04 by doc_rot »

Offline doc_rot

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Re: saving a 1980 KZ750 twin
« Reply #441 on: Jul 11, 2018, 07:26:03 »
it begins...

Online irk miller

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Re: saving a 1980 KZ750 twin
« Reply #442 on: Jul 11, 2018, 09:21:04 »
You don't have oil running up and around those studs do you, Doc?  Usually the studs that have the rod between the threads machined smaller than the threads themselves are running through oil passages, so oil flows passed them.  Oil leakage is usually due to the o rings or gaskets that seal between the head and the cylinder.  If that's the case, you're blocking oil passages with those APE studs.

Offline Maritime

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Re: saving a 1980 KZ750 twin
« Reply #443 on: Jul 11, 2018, 10:45:42 »
You don't have oil running up and around those studs do you, Doc?  Usually the studs that have the rod between the threads machined smaller than the threads themselves are running through oil passages, so oil flows passed them.  Oil leakage is usually due to the o rings or gaskets that seal between the head and the cylinder.  If that's the case, you're blocking oil passages with those APE studs.

+ 1 I was thinking the same thing. My Honda twin used 4 of the studs as oil feeds and 4 that were o-ringed off. all looked like the tapered one, when you pulled them, the 4 that were feeds came out easy, the 4 that were not were always rusted to shit and stuck.
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Offline doc_rot

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Re: saving a 1980 KZ750 twin
« Reply #444 on: Jul 11, 2018, 15:41:33 »
Thanks for the concern guys. If you look closely you'll see there is a separate oil passage on the side that runs up to the head. Its between the outer most two studs, so its all good. Funny enough though, on the z1/KZ1000, oil is fed around the outer head studs as you described. APE mentions nothing about this and I have been running these heavy duty studs in my kz1000 with no problems.
« Last Edit: Jul 11, 2018, 15:44:10 by doc_rot »

Offline doc_rot

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Re: saving a 1980 KZ750 twin
« Reply #445 on: Jul 12, 2018, 03:27:08 »
Some more info of interest to the kz750 twin owners.

taking from www.z750twin.de/zylinderkopfdichtung.htm


"Only buy the head gasket part #: 11004-1267, the green one
Itīs the last and best cylinder head gasket for the 750 twins

A little gasket history :
11004-071 => 11004-078 => 11004-1055 => 11004-1267
11004-071, recall campaign in June 1976
11004-078, the red one with black middle section
11004-1055, light brown, comes with the first LTD model
11004-1267, the green and the best for the last LTD model"

Online canyoncarver

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Re: saving a 1980 KZ750 twin
« Reply #446 on: Jul 12, 2018, 11:49:44 »
That's great info.  Now I'll have to check and see which ones I have.  Google Translate to the rescue.
--

YZF750/1000R The Fly
KZ 750 Twin
ZRX 1100
KZ400 The Rabbit
65 Norton, My damn Shovelhead chop, and an 86' FXR
more YZF750R's, the KZ's, a Zephyr750...and the unfinished 75' CB550 cafe.
--

Offline beachcomber

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Re: saving a 1980 KZ750 twin
« Reply #447 on: Jul 12, 2018, 12:26:23 »
Small update, but one of particular interest to kz750 twin owners.

I was cross referencing part numbers and realized the z1/kz1000 share the same head studs as the KZ750 twin. This means you can use APE's heavy duty head studs and nuts which are intended for the z1/KZ1000. I have bought a set and can now confirm, however, you do end up with 4 extra studs and nuts you don't need. These bikes are notorious for head gasket leaks, increased compression will likely make this worse, hopefully this will help address that.

Think I'm going to need some of those for the blown motor !!
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