kz750 or gpz750 cylinders for a 650

I think a comparison of the OD of the cylinder block casting on the outside of the cylinders would be close enough. Worked well enough to determine that I could bore a 10hp Kohler K block to the 12hp dimensions anyway

Ahhhh the plot thickens. I took a look at Mark Wing's 2 different blocks, the 750 on top and the 650 on the bottom. The 650 has the slots for the cams roller shafts notched into the cylinder casting, but the 750 is clearly different.

Here is where it gets puzzling.

I have what appears to be 1980 750 cylinders that are at the shop being bead blasted and bored for the 810 kit. This block has the exact same notches for the rollers as my 650 had. I even tried the 650's rollers and they fit perfectly which is good as I am looking to retain the 650's cam chain set up, but swap the sprockets onto the Kz750 cams.

My block has 738 (if my memory serves me correctly) cast into the block. I cross-referenced the roller part # for the '77 650 and the '80 650 and they are the same. I took a look at the parts diagrams and they look identical as does the 1980 750 cylinder diagram which shows the notched area for the roller shaft...same as the 650.

What I am thinking is that in the early run of the 1980 Kz 750/4 Kawasaki must have used the same cylinder casting as the 650 but simply changed the cam chain assembly from single roller to Hy-Vo and then later changed the cylinder casting slightly for the new cam chain set up.

The 1980 cam chain assembly diagram for the 750/4 shows a completely different cam chain set up than the 650. I don't have the parts in my hand to check, but does anyone have any thoughts on this possibility? I am thinking that the cylinders that Mark took a picture off might be from later than 1980 when Kawasaki changed the casting. If this is the case it would also prove that the 650 casting could handle the 750 sleeves-right?

Cheers-Colin Firth-Ontario Canada

Post edited by: reborn650, at: 2006/04/06 15:25

Post edited by: reborn650, at: 2006/04/06 15:29

reborn650 wrote:

Ahhhh the plot thickens. I took a look at Mark Wing's 2 different blocks, the 750 on top and the 650 on the bottom. The 650 has the slots for the cams roller shafts notched into the cylinder casting, but the 750 is clearly different.

Here is where it gets puzzling.

I have what appears to be 1980 750 cylinders that are at the shop being bead blasted and bored for the 810 kit. This block has the exact same notches for the rollers as my 650 had. I even tried the 650's rollers and they fit perfectly which is good as I am looking to retain the 650's cam chain set up, but swap the sprockets onto the Kz750 cams.

My block has 738 (if my memory serves me correctly) cast into the block. I cross-referenced the roller part # for the '77 650 and the '80 650 and they are the same. I took a look at the parts diagrams and they look identical as does the 1980 750 cylinder diagram which shows the notched area for the roller shaft...same as the 650.

What I am thinking is that in the early run of the 1980 Kz 750/4 Kawasaki must have used the same cylinder casting as the 650 but simply changed the cam chain assembly from single roller to Hy-Vo and then later changed the cylinder casting slightly for the new cam chain set up.

The 1980 cam chain assembly diagram for the 750/4 shows a completely different cam chain set up than the 650. I don't have the parts in my hand to check, but does anyone have any thoughts on this possibility? I am thinking that the cylinders that Mark took a picture off might be from later than 1980 when Kawasaki changed the casting. If this is the case it would also prove that the 650 casting could handle the 750 sleeves-right?

Cheers-Colin Firth-Ontario Canada

Post edited by: reborn650, at: 2006/04/06 15:25<br><br>Post edited by: reborn650, at: 2006/04/06 15:29

My kz750 block (not sure of the year, the ebay advertisment said 88...) has the 0.738L casting on the side, and my 650 cam chain stuff (roller chain) all fits in it too. I have the kz750 cams Ill be putting in by swapping the cam sprockets. besides enlarging the top case to fit the larger sleeves, its going to be a bolt on mod. (besides the overbore for the 810 kit)
Ill try and get some pics of it in a couple days if I can borrow the dig cam again....

Post edited by: 77KZ650, at: 2006/04/06 15:47

I have one 80 750 cylinder block and 3 83 GPz750 cylinder blocks in the garage, so I just walked out to look at them.
The 80 750 cylinder block does indeed look like the 650 block in the bottom picture, while the 83-85 GPz750 cylinder blocks look like the top picture.

Now I wonder when the change was made, anyone have an 81 or 82 750 cylinder block they can check?

Maybe the GPz750 cylinder blocks are the only ones that look like the top picture?

Hmmm.

I did some 650 research on buykawasaki.com, and it indicated that some 81 models had the HyVo cam chain, and all 83 models had it, I don't remember whether some or all 82 models had it though.

Post edited by: steell, at: 2006/04/06 15:55

I do have another 750 motor but not what year is and it's not taken apart to check.
The top block I think came from a Spectre

steell wrote:

I think a comparison of the OD of the cylinder block casting on the outside of the cylinders would be close enough. Worked well enough to determine that I could bore a 10hp Kohler K block to the 12hp dimensions anyway

The cooling fins are bigger on the 750 but the main part of the block seems to be the same size

Mark Wing wrote:

The cooling fins are bigger on the 750 but the main part of the block seems to be the same size

So it looks like it would work, but it may not be a desirable combo as it may run a bit hotter?

Just drive reeeeeeeal fast and it won't overheat:)

Cheers-Colin Firth -Ontario Canada

'77 Kz 650 Custom - (Miss July on 2006 Kzr Calendar,) Wiseco 810 kit, Kz750 cams, Kz750 intake valves, 750 GPz springs, Ported head, WG Mikuni 28's, Filters, Dyna Ignition and coils, MAC pipe, 13 tooth sprocket, 130 Rear Spitfire Tire. Going back to original '77 Moon Dust Silver. Goal is to have a stock-looking bike that will tighten up any loose dental fillings off the light.