4 valve head swap?

I have been thinking about this all day (at work)

this thread talks about zx900 rods having the same big end as a kz650, and being 4mm longer (depending on what heigth I need they may be useful, maybe not...) and having a 17mm small end.

kzrider.com/index.php?option=com_kunena&...mit=20&limitstart=40

Does anyone know what size the small end on a 1989-90 zx750 is?

It is just hard to get the numbers I need (con-rod length, piston pin sizes

Injected wrote:

That's a bit much on the pic's... I don't want to high-jack this thread and make it about my bike - then you throw in Noard's bike? (which is a turbo motor!)

I think we should keep the perspective of the 4V head swap experiment and not shift it onto drag bikes or race motors.

If anybody needs to see pic's of my stuff they should go here:

www.cyclemadness.com/cmforum/index.php?topic=507.0

www.cyclemadness.com/cmforum/index.php?topic=550.0

If you are using your bike as a referance in this thread, can't we see the referance?

Sorry for any HiJacking!

using the carrillo catalog I have found these bikes have the same big end as a kz650 (1.4963) 38.006mm

kz650 length (4.213in) 107mm

GSX-R1000 '01-04 small end: 16mm length 111mm
GSX-R1000 '01-04 Stroker Small end: 16mm Length 109mm
GSX-R1000, '05-08 Small end: 15mm Length 111mm
GSX-R1000, '05-08 STROKER small end: 15mm length 109mm
GSX-R1000, '09-10 Small end: 15mm length 112mm

I would rather see pics of the ZX head and barrels running on the 650 bottom end...

I don't want anybody to get too distracted with the drag bike - the whole idea of this thread was the 100hp street version of a KZ650... Right?

I just used mine as a reference to show it could be done as a race motor and I did not offer up the pics myself - no harm done, plus the guy who started the thread asked for them anyways...

I would really like to see what dude comes up with.

Disregard all the info in my earlier post...

the gsxr1000 rods are 2mm more narrow on the big end side (kz650 rods are 22mm thick while the gsxr1000 rods are 19.9mm thick)

Unless shimming a rod is a possibility (I have bever heard of it, but how knows :blink: ) the big end is just too thin to use.

Injected wrote:

I would really like to see what dude comes up with.

Probably alot of nothing

Wiseco catalog doesn't list the ZX750 until 91, and it says the 91 uses a 18mm pin.

So is the thought of bushing the stock ZX piston for the 650 pin looking attractive?

I think that 3mm difference is a perfect size for a bushing... anything smaller might be too hard to assemble.

here is a post I read on the zx forum, the member mentions the differences between the 91 and later and 90 and earlier pistons (he used the 92 pistons as a big bore kit for the 90 cylinders). It mentions that the small end of the rod had to be bored out some. If this is correct, I would think 90-89 zx7's have a 17mm piston pin.




Well the 92' pistons are 3mm larger so the machine shop bored the cylinders to fit the pistons, the 89' rods had to have the small end machined to accept the piston pins from the 92 pistons. The 92' piston pins are slightly larger. Also the underside of the 92' pistons had to be machined as the small end of the 89' rod is slightly wider. The bottom side of the cylinder had to be machined because the distance from the top of the piston to the center of the wrist pin is slightly shorter. As for using the 90' cams they are just 1mm taller meaning the valve lift is more but, I had to reshim the valves. The stock valves are used, I believe the 89' and 90' valves are the same size. There is a little room for larger valves but the cost was more than I was pepared to pay the benefit wasn't worth the exspense. I did port and polish the intake and exhaust ports, and port matched, and I had the head shaved too. By the way after machining the undersides of the pistons they were the same weight as the 89's. Everything was balanced; rods, pistons, pins. Some of the maching I did and other stuff like having the rods resized, boring, head shaved was done by the machine shop. Having all that meat milled out of the cylinders lightened the cylinder by about 10 pounds. I don't have the specifications handy, they're written down somewhere. I ran the engine for a year, it did run very well and I still have it, but I've moved on to another project. I found getting parts for that motor is very difficult especialy water pumps. I am currently putting a 99' zx7 engine in that chassis. Then if money is abundant I would like to bore and stroke and port etc. I built a excell program for determining engine potential and horse power output with various mathematical formula, and the 89' had to much stroke to produce the output I would like and the 96' plus motors are a better bet, also parts are abundant.

The cylinders finally showed up at the shop and my buddy had good and very bad news for me. The good, the blocks are the exact same height so my rods would work mint, in effect it would be a stroked zx750.

The bad.... the blocks are not even close to the same. He tells me he can do it if I want by cutting the block and spacing 2 and 3 out by about 3/8" then welding up all the stud holes on the upper cases, building up new bosses on the inside of the cases by welding then drilling the new stud holes... he thinks the hardest part will be adding length to the cams. I am now wondering that the cylinder spacing on the kz550 is...

I trust this mans work, enough to throw a let over it and rev it to 12,000 rpm's without a second thought, so if he tells me he can do it, I am sure he can. But what I am trying to work through with him now is, will all this work be worth it? Water cooling and 4 valves is hot shit... but the scale of this mod may just be beyond what I am looking to do.

So... What is the goal?

Get back to K.I.S.S and get away from the horse shit of using a end driven cam head.

It occurs to me that if you want to adapt a 4valve head onto a 650 motor and increase displacement then look at an old 600 Ninja head from 1985. Center cam drive. No idea on spacings but wouldn't be surprised if it was pretty close.

Also 87 zx750, center cam drive.

If that's doable, use the ninja cams and have them hardwelded and ground to suit. Cam sprockets shouldn't be too difficult to adapt from the 650.

Also, I would get some measurements on some old Suzuki GSXR oil cooled 750 heads and see if grafting that might be possible.

Get 750 jugs, bore to 810 and price some custom made 4 valve pistons.

Put the biggest valves in the head you can make work, inject the motor....

JMO