Whelp! I found the problem.

Oh, and one other thing, I know there might be some of you thinking “well why doesn’t he just buy the pretty custom red Zephyr with a good motor, and get rid of the old Zephyr?” 

And you know, I am asking myself that question, too. But so far I just can’t let my old Zephyr go. I have loved that bike for so long, have so many memories on it, and the night it died I vowed to fix it. I have such a hard time not being emotional about it. 

wow, decisions decisions !!!!!!! That is a nice looking bike to buy for the motor. Any second hand motor is a lottery but at least if you can find one from a bike breaker it should come with some kind of warranty

That’s the other… other… fourth option element to all this. Just buy the pretty custom red Zephyr and finish it and ride that? Would be pretty sweet, I’m sure. But then my beloved original Zephyr would still be in the same pickle. 

Too many choices. 

Analysis paralysis…

Probably the most straight forward choice would to get a 1984 or later zx550 motor. It has the peak of what Kawasaki could squeeze out of the 550. 
The problem I found is that it only makes sense to buy a know running motor, which usually means you have to buy the whole bike to get one. 
I couldn’t afford to buy a whole bike, so I bought a “running” motor ( was sent video of the motor in the bike running ) and it arrived with a rod welded to the crank.  So I put the higher compression pistons and the better cams in my zx500 motor. 
And I love it. I simply love it. 
But in the process of restoring my bike, I struggled for years to find parts to replace the damaged ones I have. So I found a zr550 that only had 3,000 miles on it, but it had sat since 1995 and irreparable title issues. So I bought it for all the spares. And I found it’s easier to store a motorcycle in pieces and can be carried up stairs and stored out of the way. So I have low mileage engine but that sat for 32 years and will probably need all new gaskets before it could be started. 
But….I highly suggest buying the Red one and keeping your old one for spares. Considering the cost and rare possibility of even finding a zr550 fuel tank is crazy. They are all rusted inside. All of them. (Except for my spare….its factory clean inside)  Or….maybe down the road, you will stumble on another motor and you can put your original bike back on the road. The possibilities are endless. 
I am just obsessed with building a zx600 to maybe put in mine. So I will always support doing that to. 

Daftrusty post=923965 userid=25983
Probably the most straight forward choice would to get a 1984 or later zx550 motor. It has the peak of what Kawasaki could squeeze out of the 550. 

Not to be a Debbie downer but good luck finding a zx550 motor. i had to make compromises for my zx550 from lack of parts and ended up putting lower compression pistons in my bike, opposite of what you did. Lol. Location may make a difference in availability though. I think the zx550 engine looks better, although I may be biased.
 

StereoOrdinary I want to help you and get parts out of my way. I have an old 1985 gpz550 crankshaft, primary chain, crank bearings, and many other engine parts. 

If you are interested in rebuilding the engine, I can ship them to you if its within your budget to pay for the shipping. I can also take any measurements if you're interested.

I want to relieve you of at least some stress!     

That would be amazing, thank you for the offer! I would be interested in the crankshaft, primary chain, cams, and any con rods and bearings you might have. I would probably want to pass on other large items like cases and covers. I’ll shoot you a private message and we can discuss the viability of shipping these parts. Thanks again! 

Huge shoutout to Craig aka Bound for hooking me up with a crankshaft, primary chain, and four good con rods for my project here! I love this community! 

I have had to put the project on hold for a little while. The engine stand I was borrowing had to go back home for some amount of time. Admittedly I don’t know what I need to be doing next anyway, so I’ll be doing research and talking to folks and trying to figure out what I need to do to fit the new crankshaft and so forth. The cost of all the gaskets and o-rings and such that I need isn’t overwhelming. But I did purchase another project bike, so I’m balancing a number of spinning plates right now. Will keep you all posted!