Thank you guys again for the positive support.
It has been awhile, but I have finally made some progress....
So my cylinder bores were worn way beyond the service limit after 27,000 miles.
This forced me to decide whether I wanted to go the 810 over bore or try to buy a used cylinder head and 9.5:1 pistons online that may or may not arrive worn past its service limit. I had already gone this route before when I was putting gpz550 pistons and cams in my zr550 and it turned out to be a nightmare of getting e-screwed with numerous unusable parts. So after a year of researching the Cruzinimage pistons kits, I decided to give them a try. (Yes…I know…I know….)
Disclaimer:
This is me documenting my experience with these particular piston kits. This me not yet saying that they are of good quality and people should buy them, only that I am trying them for my own reasons. ( I simply cannot afford the Wiseco kit.)
Because I couldn’t find kz owners who have used these and could give an opinion, I have literally read hundreds of threads on Honda and Yamaha forums regarding the Cruzinimage kits and virtually every consensus was the same:
”Inspect them for sharp edges and file them down” and “I have been running them for a xxxxx miles and have had no issues.”
This gave me the confidence to try them on my project and will see how they hold up.
The pistons look very respectable and were packaged very well. No scratches or flashing or sharp edges on the milled areas. They are essentially stock 9.5:1 pistons only 3mm over sized, but with my smaller non-quench chambers I will still have close to 10.5:1 compression.
Compared to the stock 9:1 pistons.
The head gasket is a MLS type that looks identical in construction to the OEM Kawasaki gasket I used on my zr550.
I made the point of finding an engine machinist that was motorcycle specific to do the cylinder boring, as I wanted there to be no question of the quality of machine work since I was using unproven pistons. I finally found one that had 30+ years of motorcycle machine experience and was in the Minneapolis area. They had worked with the Cruzinimage pistons before and reported they were that they “never had a issue with them” which is a high praise since they are a Wiseco dealer.
Once they had bored and matched the pistons to .045mm clearances, I had to gap the rings myself and all of the rings required no adjustment as they all were within the factory specs.
*I did have one oil control spring that wanted to overlap ends when I installed it on its piston. I fiddled with it for an hour before I was sure I had corrected the issue, but I am not 100% convinced that the spring didn’t try to overlap itself once I had the piston in the bore. This has kept me literally kept me awake at night and only when I have the engine running and it doesn’t blow blue smoke will I be able to relax.*
Installing the pistons is my most dreaded task of the entire bike build. ( I once had an oil control ring pop out upon installation and irreparably damage a cylinder bore.) I used the hose clamp and plastic strap style ring compressor and after what seemed like a hundred stops and starts got all the pistons into the bores without damaging anything. Deck height is right at 0 when using the weird single layer metal base gasket that I got from Kawasaki (I ordered the one for the 81 kz750e and this is what they sent me.)
Here goes nothin....
Finally together
OEM metal base gasket
Once that was done, I now had to determine if the pistons would make contact with my non-quench cut head. I had posed the question in a separate thread if using 9.5:1 or 69mm pistons in a non-quench head was possible, but no one was able to deny or confirm if it was possible. So I made some clay strips and placed them in the bores, torqued down the head down and and spun the piston up and over TDC, removed head and measured. Thankfully I have a .044” quench ring clearance and gap between the piston dome and lip of the chamber. The quench ring varies from 7mm wide on the sides to 5mm at the valve pockets which hopefully will help keep down the risk of detonation and help with squish effect mixture circulation.
I’m just relived that nothing collided.
Non-quench cut chambers in question