saving a 1980 KZ750 twin

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.
 

Attachments

  • IMG_0879.jpg
    IMG_0879.jpg
    702.1 KB · Views: 267
it begins...
 

Attachments

  • IMG_0880.jpg
    IMG_0880.jpg
    1.8 MB · Views: 251
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.
 
irk miller said:
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.
 
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.
 
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
It´s 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"
 

Attachments

  • IMG_022820Medium.jpg
    IMG_022820Medium.jpg
    59.5 KB · Views: 238
That's great info. Now I'll have to check and see which ones I have. Google Translate to the rescue.
 
doc_rot said:
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 !!
 
Finally got around to making mirrors for this thing. I got these cheap mirrors off ebay for $20, they are actually pretty nice, solid aluminum construction and convex glass. I used the old head studs for the stems, turned a little cap where the mirror attaches, tig brazed it on, and polished it back. I also had some stainless flange nuts that I trimmed down so they wouldn't be so bulky.
 

Attachments

  • IMG_0930.jpg
    IMG_0930.jpg
    2 MB · Views: 248
  • IMG_0932.jpg
    IMG_0932.jpg
    1 MB · Views: 238
  • IMG_0939.jpg
    IMG_0939.jpg
    1.2 MB · Views: 244
  • IMG_0940.jpg
    IMG_0940.jpg
    1.2 MB · Views: 249
  • IMG_0944.jpg
    IMG_0944.jpg
    1.6 MB · Views: 256
Very cool way to repurpose those studs 8)

Not sure whats going on in the sketch in the background but I like it.
 
that's an old painting of mine, as you can see its being absorbed into the scrap wood pile.
 
Help please. I need to know the outside diameter of the front wheel axle sleeve nut.

The guy modifying my Grimeca spindle needs the measurement. As you know the fork caps have a gap one side when torqued up and I've been given different diameters so far ! ::)

My thoughts are if he makes the sleeve spacer the same diameter as the original sleeve nut - it HAS to be correct ! ;)
 
Im out of town for a couple weeks, let me get back to you when i get home.
 
beachcomber said:
Think I'm going to need some of those for the blown motor !!

Also make sure you have a copper headgasket made or at least have the cylinder piano-wired.

A Z750 Twin is one of those bikes that have been on my list for a while...
 
der_nanno said:
Also make sure you have a copper headgasket made or at least have the cylinder piano-wired.

A Z750 Twin is one of those bikes that have been on my list for a while...

The plan was for wire ... copper head gaskets are astronomical to have made ! The bottom end looks pretty bulletproof - with some decent rods and pistons ... half way there ! I've secured 3 heads now - so I'm looking at getting a jig set up for twin plug conversions. Not a huge market, but they ARE starting to get popular now. What's donor prices like over there ?
 
Well if you have a CAD-drawing, a copper head-gasket should be within 20 to 30 Euros at my waterjet cutting place. I agree that cometic charge rather handsomely for proper headgaskets though.

Donor prices? Well you wouldn't want to know. 1500 to 2000 Euros, I'd say. It would be cheaper to import them from Germany and go through the legal process. I could probably get one for approx. half the price (and that's including about 200-300 Euros of taxes and fees...)
 
der_nanno said:
Well if you have a CAD-drawing, a copper head-gasket should be within 20 to 30 Euros at my waterjet cutting place. I agree that cometic charge rather handsomely for proper headgaskets though.

Donor prices? Well you wouldn't want to know. 1500 to 2000 Euros, I'd say. It would be cheaper to import them from Germany and go through the legal process. I could probably get one for approx. half the price (and that's including about 200-300 Euros of taxes and fees...)

Thanx for the headsup Greg. I could spend months here in the UK just trying to find someone to do the job! I'll contact you nearer the time. Thanx
 
beachcomber said:
The plan was for wire ... copper head gaskets are astronomical to have made !

Have you contacted Lani at Coppergaskets.us? I've never felt his prices were bad. Should be in the range of $40 - $50.

https://coppergaskets.us/
 
irk miller said:
Have you contacted Lani at Coppergaskets.us? I've never felt his prices were bad. Should be in the range of $40 - $50.

https://coppergaskets.us/

Thanx Irk - but carriage from the US is a killer !!! It's approximately TWICE the cost of sending stuff from UK to US. There's loads of bits I want - cheap enough .... until you add in the post.
 
Back
Top Bottom