full bore build, with pics. turbo, efi, 810.

Hello, so I've recently posted a few pics and questions regarding my 2 kz650's. My hippie was that I could get the 79 to run well enough to ride while I finished some other projects (h2, titan, tr750) but I did a compression test today and the numbers were not good. 55, 90, 75, 85.

This explains why I couldn't get the carbs to function properly on the bike.

So here is the build. After tons and tons of reading, I decided to do a full bore build.

I got ano 83 gpz1100 efi for 120 on the bay.
Then I got a gpz turbo 750 crank with rods for 120. The rods have 18k miles. I plan on punching it to 810, while doing a turbo and efi. I'm undecided on suspension.

Honestly I really love the look of these old bikes. Kawasaki really built some good looking bikes in the 70's. Because of that I'm not sure what changes I want to make (if any ) to the suspension. The frame will get braced by bridge city cycles here in Portland.

Questions

1, the 810 kit need the top end to get bored out. Can I just bore my 650 cylinder or do I have to do the 750 top end? I didn't find this answer on any of the build threads.

2, is there a better choice motor to use based on year? 79 or 80? The chain ruler cam is the only difference right? If so then it really shouldn't matter is think.

I was toying with putting a 636 or gsxr600 in one but I decided that the motor had to remain Era correct.

Pics in 5. I have to get out to my garage and start wrenching.

3,

This is the beginning. I'll break into her tomorrow.

You could always have your 650 block bored to fit 750 sleeves,then have it bored for the 810 kit it you want to be sneaky! :laugh:

So with the 80 650 motor I won't need to bore out the top case to receive the 750 jugs right?

You might want to head over to KZ650.info there are more people modding their 650 engines over there than here. Here is some info i lifted form a turbo efi thread
Thread is here > forums.kz650.info/index.php?topic=3359.0

"Interesting Facts, Re Head swapping z750 heads/cams/stuff

Valves are bigger in the 750 head.
z650 head 32/27 (in/ex)
z750 head 33/29
As are the intake runners, but I don't have the 650 head to measure currently, but definately by a couple mm (3-4 off hand, I measured once)

Combustion chamber volume is similar enough to be irrelevent. (esp if machined)
650 23.3-24.1cc
750H 24.8 +-0.4cc
750L 25.3
Gpz750 25.9
Turbo 24.6

Cam heights. (in mm)

z650 35.73-35.87 (both)
z750 36.245-36.353 (both) So 0.5 more lift!
gpz750 36.746-36.854 (in) (So 0.5mm more again)
35.746-35.854 (ex) similar to 650, but longer duration. 286 vs 260 (Or 262 on the F models)

Turbos have 650 cams.

Also BEWARE, SOME camshafts/head have a different base circle diameter most are 1.100" some are 1.070, rare ones are 0.900!

z650s have a differnet 5th gear ratio than 750s. 24/27 (750 21/24) Discovered this one long ago. Turbos are completely different.

early z750s (E/H) ran Keihin CV34 carbs.. later ones and Gpz ran Mikunis BS34. I had a set of Keihins for years- Excellent carbs (Have 2 sets spare)
One reason is the Keihins run a Primary and Secondary Main Jets. Mikunis have One.

KZ700s ran a 64mm piston. (66 for 750, 62 for 650) Sounds like a suitable alternative to a Wiseco kit. Same size...

Turbos have a 16mm Gudgen pin (wrist pin), instead of 15mm. And flat top pistons.

Early GT750s have a little hole in the conrod, that squirts oil under the pistons, and onto the cylinder wall.

also if you haven't already, check your PMs

PLUMMEN wrote: You could always have your 650 block bored to fit 750 sleeves,then have it bored for the 810 kit it you want to be sneaky! :laugh:

Sounds like the best way to me. I bought some 1015 barrels for my Z1. Barely fit but now I have plenty of room and it runs cooler. Will the 750 barrels fit into the 650 block?

Just in case it would help, I have a near complete KZ750E engine for parts. Cylinder, head, cams, etc. I also have a brand new 810 kit I'm unlikely to use. Drop me a PM if any of this stuff would be of use to you.

Stuff arrived. Gpz efi and turbo crank