THE Z2 WAS IDENTICAL TO THE LARGER BIKE IN DESIGN EXCEPT FOR THE DISPLACEMENT OF JUST 746 CC AND SMALLER 26MM CARBS.
IT WAS ONLY OFFERED IN THE BROWN AND ORANGE COLOUR OPTION FOR THAT YEAR.
ENGINEER INAMURA DECIDED THAT SIMPLY REDUCING THE BORE SIZE OF THE Z1 WAS NOT GOOD ENOUGH. INSTEAD KAWASAKI CHANGED THE BORE AND THE STROKE TO 64MM X 58MM. THIS CHANGE REQUIRED A DIFFERENT CRANKSHAFT, CYLINDERS, PISTONS, PINS AND RINGS. THE REST OF THE MOTOR REMAINED THE SAME.
Dave Marsden also said:
"I HAVE LISTED BELOW THE MAIN PARTS THAT WERE DIFFERENT FROM THE 1973-1975 Z1 RANGE OF MODELS:
Nothing useful there. Of course the part numbers are different. The cam chain is the same as the Z1, the wrist pins are both 17 mm, The sleeve OD is the same. What I need to know is the Marking codes on the crank and rods. I will need them anyway if I decide to sell the crank.
An old friend of mine's Dad has a beautiful, (original) 1967 SS/RS Camaro that he bought brand new...He gets absolutely FURIOUS when some "know it all" at a car show tries to tell him what he's got.... under the hood or anywhere else on the car...the "takeaway" from this (for me) is that IT IS HIS VEHICLE, HE OUGHTTA KNOW WTF HE HAS...Cheese on rice, let this one GO already! LOL!
Hey Grumpy, haven't talked to you in a while. I'm taking the opportunity to document my build. I didn't get all the pics I should have. The crank is one of them. I was actually done a favor. It may be the 750 crank is a waste and I'm loosing ponies for it. I didn't realize just how valuable it is. I'm looking at it as a experiment. 903 cranks are easy to get. I had one but one of these low lives cost me it by burning down my shop.
"When it rains lemons, make lemonade.
Being the stock 1015 pistons are only 2 mm lower on the deck height and the 10.25/1 were even, I suspect the crank throws are different and the wrist pins are as well. There's only one way to find out for sure. I found a stock 903 piston and will compare it to the 10.25's but that won't tell us anything about the 750's. I'm going to send john a e-mail to see what he can provide.
wiseco list a 70 mm bore as standard for 1015cc's
and we have established z2's have a 58 mm stroke
which gives us 893 cc's
rod length doesn't figure in to an engines size.
a formula using bore and stroke determines engine size.
Leon, yes I used a bore of 69.4 mm which I got from www.motorcyclespecs.co.za when calculating the cylinder volume; (pi)*(3.47)sq*(5.8) then times 4 (four cylinders) = 877.60 cc . That is how I ended up with the 877.60 cc. If would have used a 70 mm bore the formula comes up with 893 cc. For a K1000, using a 70mm bore with a 66mm stroke the formula comes up with 1015. So not sure why that website states 69.4 mm for the bore on a KZ1000.
Leaving that aside, yes the throw of the crank is what is going to determine the stroke (height of the cylinder). My question is though, given the stroke is shorter, does that mean longer rods would need to be used in order to get the compression back? Are the 750's rods longer than the 900 rods in order to compensate for the 8 mm difference in throw? Thereby achieving the same deck height? Just curious on how Kawasaki did it.