TOPIC:

why would anbody want to put a Z2 750 crank into a Z1 ?what are the benefits?

Lighter, spins faster. Why would someone put in a 810 kit and not a larger one? Could it be because of plain bearings?
Steve
Your move.

the plain bearings have nothing to do with it .its limit is based on sleeve thickness and block .you would have to bore out the block and put thicker sleeves in.its been done many times.

a Z2 crank has a stroke of 58 mm . a Z1 66 mm how is that going to help?

That's what the spec says. In fact when assembled there is only 4mm drop in deck height. With the 10.25/1 pistons, the deck height was even. That didn't become apparent until I installed stock 1015 pistons when I ruined one of my 10.25 new pistons. I had cast ones before. Yes I can and probably will have the bottom of the barrels shaved to compensate for this. Maybe not. It's the flywheel effect or lack there of I was going for and it worked for many years. I had my 900 crank when I put in the 750 and there was a noticeable improvement.
As for the barrels. The 903 barrels had a tendency to over heat. The 1015 barrels don't. There's enough room for a larger overbore. The sleeves just barely fit into the block. All and all I've been very happy with this set up.
Roller bearings do make the difference. That's why the Z1 and KZ 900 engines were and are so popular.
I was disappointed when I learned Kawasaki went to plane bearing lower ends like the Honda's of the day on their smaller fours. I've seen many bikes for sale for cheap because of "spun" bearings or worse.
I also believe that is the reason my Z1 is still on the road 40 years later and many more just like it. The crank coupled with the Babbitt cam bearings insure the longevity of this design and will for more decades to come.
Steve

do the math 58 mm stroke 66 mm bore =793 cc 58 mm stroke 74mm bore = 997 cc . so what is the displacement of your engine ?with the Z2 58 mm stroke crank? deck height and compression ratio are calculated differently.deck height wil affect compression ratio. combustion chamber size will affect compression ratio. bore and stroke determines engine size.what size bore are you running ?

There you go again. (Ronald Regan)
I just explained that.
Steve

so you can,t figure what size motor you are running with a 58 mm stroke ?

The stock 903cc has a bore and stroke of 66 X 66mm. The 1015 is 66 X 70mm.
Steve

yes that is true but you put in a Z2 750 crank = 58 MM STROKE. 70 MM BORE = 892.9 CC

The Z2 has a bore of 58mm and a stroke of 64mm. I was off by 2mm. I didn't measure it, So shoot me.
The fact is,,,,the Z2 crank is lighter than the 903 and the KZ 1000 crank is heavier than both thus less flywheel effect. Your figures are off. Thank you though, I just looked it up and I only have to shave off 2mm. Not likely.
Steve

If anyone is interested, I'm getting my figures from Kawasaki Z1.com
I have a profile there as well.
Steve