4 valve head swap?

I have been told, that if you line a kz750 head gasket up with a zx750 head gasket (86-90) the stud holes line up.

This got me thinking, what would it take to adapt a zx750 head and cylinders. The zx750 is water cooled so a rad, water pump and some other goodies would need to be fitted but that is no biggy... also oil lines would need to be come external again no biggy. Custom pistons would be needed, expensive, but not that much more coin than a 810 kit. Maybe custom rods as well.

Does anyone have a zx750 of the correct vintage? (or better yet a head/cylinders from a zx750). It would be nice to make sure before I but a head that the studs are indeed the same.

Anyone ever looked into this before?

just the other day I read a comparo of the 83 GPz750 and GS750. The suzi is 16 valve, and I thought it would smoke the GPz in engine performance, but the kawasaki only had 1 less hp (85 vs. 86) and had far more torque...the kawasaki won the comparison. Maybe just tuning the 8 valve engine as good as you can would be a simpler idea...?

The 1989 zx750 was listed as 107hp. Compared to the 91 hp a 1985 gpz750 is listed at that is a fair gain. It is also a massive jump from the 62 that a kz650 is listed at. Also water cooling would let you the use 13:1 or better compression. Also the 4 valve heads can rev higher do the the lighter weight of the valves.

It has been discussed a few times and the limit of the 650/750 motor always seems to come back to the two valve head. I am sending some messages around on a zx forum trying to collect some parts cheap like.

Perhaps a Rochester Quadrajet would just the ticket for this engine..... :silly:

The ZR750 Zephyr head is to the KZ750 as was the 83 GPz1100 head to the KZ1000. It is still a two valve head but much bigger valves and the ports have better flow.

otakar wrote:

The ZR750 Zephyr head is to the KZ750 as was the 83 GPz1100 head to the KZ1000. It is still a two valve head but much bigger valves and the ports have better flow.

The ZR750 Zephyr (91-92) uses the same valves as the early 750's.
The 2001 (and associated years) ZR750, aka ZR7S and ZR7 use different valves than the rest of the 750's.
So is it safe to assume you are referring to the 2000+ ZR750 and not the Zephyr?

Do you happen to know the valve sizes? It's hard to see how the valves could be much larger, since the bore diameter is still the same.

Well I took the plung, I spent $50 on a zx750 cylinder block on ebay. I will see how the studs and cylinders line up.

If they match I will have to sort out rod length next (maybe a base gasket spacer maybe longer rods...who knows!)

Then I will pick up a head and pistons and go from there... it will be alot of work; but I have a crack machinest/mechanic/welder/drag car builder/friend at my disposal.

i'm thinking if it could be done then someone, somewhere would have done it all ready.
i see a custom one off cam chain, cam sprockets and all related Components in your future.
then your into the water cooling aspect.

now some of us here have been here awhile and read some of you previous posts. i think we can all know what your after.
i do admire what your trying to do and your vision but i have to ask this.

is it really worth it?
we know you want a one of a kind motor that no one else has.
i'm not trying to discourage you in any way shape or form. hell, i'm rooting for you. i really hope you can pull it off.

Preston Tucker was a man before his time as well.

all i can offer is a hearty good luck.
post up some pictures of your progress.

If you wanted to try it on the cheap the best bet would have been to buy a $15 base gasket at the dealer.

There is a 7mm difference in the stroke between the 650 crank and the 750 crank.

Isn't the cam chain on one side and not in the center on a zx750.

I don't see it working, but good luck.

Anything fits anything, with enough work, a welder, and a sawzall.

the cam chain is in the center of the 1986-1990 zx750's and on the zx600's until mid 90's.

I see why I would need a custom cam chain, but why cam sprockets? So long as the ratio sprockets is right chain length should not matter (does taking a link out of your drive change change the rpm at a set speed?)

As for what I want, I want a honest 100hp at the rear wheel... I would like to do that without the added hassle of a turbo and no bottle. Maybe it already has been tried, maybe not!

kz650 62x54
1989-1990 68x51.5

so that's 2.5mm difference... but then rod lengths come into play and piston pin height in the pistons. It will be easier to see what I need when I get my hands on the jugs.

the biggest part about chain length is how hard you plan on yanking your chain....