TOPIC:

Well, not exactly, but it turns out there is a 16 valve Zephyr X 400 [ZR400-G] that was available in Japan till 2008. The Zephyr 550 [zr550 B] that was sold in the States is just a bored out 400, and shares many, many parts with old KZ550s. Here are the specs on the Zephyr X 400:

www.motorcyclespecs.co.za/model/kawasaki...ephyr_400_x%2096.htm

I wonder if it would be possible to switch the head on a Zephyr 550 or KZ550 with one from a Zephyr X 16 valve ZR400 G? Part numbers are not exactly the same but it's hard to tell if things would fit. I'd love to see what one of these engines could do bored out to 615cc with a new pipes and rejetting. I'm thinking such an engine could put out 70+hp. That would be awfully fun.

Here are cylinder head and piston parts diagrams for each of the models:

Zephyr X 400 [ZR400 G] (Japan model)
www.impex-jp.com/catalogs/moto/kawasaki/...ad/cg45838_1453.html
www.impex-jp.com/catalogs/moto/kawasaki/...29/cg46360_1461.html

Zephyr 550 [ZR550 B] (U.S. model)
www.motosport.com/motorcycle/oem-parts/K...550_B1/CYLINDER-HEAD
www.motosport.com/motorcycle/oem-parts/K...0_B1/CYLINDER~PISTON

KZ550
www.motosport.com/motorcycle/oem-parts/K...%2782_%2783-A3~A4%29
www.motosport.com/motorcycle/oem-parts/K...-HEAD-%28KZ550_A4%29

That's a good looking bike.To bad we did not get them in the U.S.A

You're just doing this for fun, right? Because I'm sure you know you could get a faster, lighter, better stopping, and better handling, bike for a lot less money, and a crap load less work. ZX6, R6, CBR600, etc.
The 90's models are getting fairly inexpensive, maybe even up to 05.

If you're doing it for fun (that's my story anyway), then "More Power!!"

Zaddict wrote:
www.motorcyclespecs.co.za/model/kawasaki...ephyr_400_x%2096.htm

A4%29

Scan this website. You will not believe all the cool old bikes on it!!!!

Rg500's TZ750's, XR750's and much more!!!! Been looking at it for hours !!!!

Thanks Zaddict for posting it. Good luck with your project too!!!

I'd think if you were going to do all that, you would want liquid cooling, so dropping in a ZX600 motor would be easier and cheaper, though I haven't seen that done either. If it was easy I would think someone would have done that by now.

It would be interesting to know if it could be done, but worth all the hassle? I'm not sure.

If you can get a 16v head for a reasonable price, you should go for it!
I, for one, would love to see how this works out...

Oh, I'd be doing it primarily for entertainment. But I'd rather have this bike with 70-80hp than any other for any price. I'm just completely in love with it. It's like being in love with a flat chested woman, but loving big breasts. There are solutions other than getting another wife...

There was a guy on the Zephyr Zone that did a Ninja motor swap into a 550. It was a GPX 600R. I don't think he ever got it dialed in though, and it just doesn't look as nice as the KZ/Zephyr motor with cooling fins:

www.zephyr-zone.com/cgi-bin/yabb2/YaBB.pl?num=1154896276/15

How about just putting an air cooled 750 in it?

PLUMMEN wrote: How about just putting an air cooled 750 in it?

More pain in the ass than it's worth. It's why I didn't put a 1000 motor in my 750. I could have made it fit, barely, but I'd have had to unbolt the motor to do a valve adjustment.

What I did instead was put 1100 block & pistons into the 1000 motor and built another bike around that.

PLUMMEN wrote: How about just putting an air cooled 750 in it?

Yeah, not really an option with the 550 (at least the Zephyr 550) - apparently a 750 won't even fit in the frame.

Who's our resident 550 expert here, anyway? Seems like Corey Clough knows a hell of a lot about 550's through his experience modifying GPZs. There was a guy named Adam Wade who ran a 550 forum as well but unfortunately he's no longer with us.

Yeah, I knew Adam. Goddamned shame...

loudhvx knows a great deal about 550s, and probably even more about electrical systems.