I found one...and bought it..Bath tube head

Ok, so I finally just bit the bullet and bought one..searching and searching for a good deal just never happened.   So now I have another piece of the performance
puzzle.  I realized that my 81 head just ain't worth putting any money into, as it will never really perform.  It's fine for burning up miles and doing stock restoration not much more. 

I have the 34mm FS Mic, Dyna2000 Ign, Kerker4into1...but not sure on the cam and pistons.  I want about 130hp, not sure the parts combo that will make that.  I'm sending the head straight to Cavanaugh for a full rebuild, port and polish.  Since its an 81, it burns oil from the bad bore job from the factory, so maybe do a 1170 or 1200 something big bore. 

Thoughts welcomed.

577nitro---proud owner of a hyper rare bath tub head.


 

I didn´t see the bath tube chamber in your pic. Did you get the ZX10A (GPZ1100UT) cams with the head?

wrote:

I'm sending the head straight to Cavanaugh for a full rebuild, port and polish. 

 

I've got bad news for you. Larry is no longer with us. I'm thinking of sending my head to APE. I can't find anyone who seems to specialize in kz heads the way Larry did.

but not sure on the cam and pistons.

I looked into this not long ago. It seemed like the answer was to use gpz1100 pistons with a spacer under the cylinder block to make up for the fact that the wrist pin is in a different spot.

You're sending it to who?

Larry Cavanaugh - KZRider Forum - KZRider, KZ, Z1 & Z Motorcycle Enthusiast's Forum


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Yes... Sorry to say that Larry passed away...The storys I could tell you about him... crazy. He has built me some crazy heads over the years. Im glad I still have the head on my 1327 that he did... I built that engine because of him... Someday I will have to tell the story. Right now Im gonna have a beer for Larry.

“I didn´t see the bath tube chamber in your pic. Did you get the ZX10A (GPZ1100UT) cams with the head?”


No I did not get them….I still need to figure out that part, and how far I want to go with it.   

wrote:

I'm sending the head straight to Cavanaugh for a full rebuild, port and polish. 


 

 

”I've got bad news for you. Larry is no longer with us. I'm thinking of sending my head to APE. I can't find anyone who seems to specialize in kz heads the way Larry did.

but not sure on the cam and pistons.

I looked into this not long ago. It seemed like the answer was to use gpz1100 pistons with a spacer under the cylinder block to make up for the fact that the wrist pin is in a different spot.”
Well that sucks….didn’t know that…great guy spoke to him once long ago.   I should call Gary from Spec II and check in on him, 30 years of two stroke tuning with him.  

Dang.   I guess I’ll talk to APE too.

577nitro

wrote:

I looked into this not long ago. It seemed like the answer was to use gpz1100 pistons with a spacer under the cylinder block to make up for the fact that the wrist pin is in a different spot.

That wouldn't work as the 1100A pistons use an 18mm pin and all the rest are 17mm.
 

wrote:

wrote:

I looked into this not long ago. It seemed like the answer was to use gpz1100 pistons with a spacer under the cylinder block to make up for the fact that the wrist pin is in a different spot.

That wouldn't work as the 1100A pistons use an 18mm pin and all the rest are 17mm.

 

Right. I realized my comment applies to the 73-80 engine. Is you're starting with a J engine you don't need the spacer.

Regarding 17mm vs 18mm wrist pins, these pistons seems like they are intended to be used with either 17 or 18mm pins.

"WRIST PIN SIZE: 17MM (CAN BE HONED TO 18MM)"

www.mtceng.com/pistons/kawasaki/gpz1100/

 

"Right. I realized my comment applies to the 73-80 engine. Is you're starting with a J engine you don't need the spacer.

Regarding 17mm vs 18mm wrist pins, these pistons seems like they are intended to be used with either 17 or 18mm pins.

"WRIST PIN SIZE: 17MM (CAN BE HONED TO 18MM)" www.mtceng.com/pistons/kawasaki/gpz1100/ "
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My engine is a 81 GPZ1100, so it has the 17mm wrist pins.   Here's where things get a little fuzzy for me on the specifics.   From what I understand from researching:

Because they are 17mm and the later model engines are 18mm, there is a .5mm delta some where.   If all they did was increase the hole size why would anything change length wise?
Somebody smarter than me needs to clarify.  Is the rod the same length between the early and later engines?  if the rods are longer on the earlier models then you would want to shim the base of the cylinders so that there would not be any interference.  I'm just guessing here....

577nitro.

I am assuming (always dangerous) that the straightforward solution to this is to use the crank and rods (or at least the rods) from the later engine - if you can find the necc parts ?

Not sure if this helps but I was running a Z2 750 crank thinking it was lighter so it would spin faster. As it turned out it has a stroke of 58mm as opposed to the 66mm on the 900/1000's. They didn't make shorter rods, they moved the locations of the pins. The piston wrist pins were in a different place too. I've heard honing the wrist pin holes work well. 
Steve