Why are there two kz1000 motors?

Depending how you view the Z1/KZ900/KZ1000 engine there are 4 main variants of the engines (and a few additional variants).

Z1/KZ900 - The 900 engines rev very quickly due to their lighter crankshaft. The crank has 'pork-chop' flywheels, and is considerably lighter than any of the 1000 cranks.

KZ1000 (77-78) - very heavy crank - full circle flywheels across the crank. Kawasaki beefed up the cases, and made minor improvements to transmission. Kawasaki retained the same stroke, just increased the bore from 66mm to 70mm. The same head design was used, so there was a 4mm 'squish' zone on the combustion chamber.

KZ1000 (79-80) - aka Mk II - beefed up center section on the crank using 16 teeth on the center section. intermediate weight crank - roughly halfway between the Z1 and early KZ1000 cranks. The cases were beefed up again in 80. 1980 is generally considered the strongest of the engines - and the most sought after for racing / high-performance engines. In the USA, the 79 was the first year of the engines to have smog ports on the head. The stator design changed.

KZ1000 (81 and up) - AKA J Motor - composite guides replaced cam idler sprockets. Transmission changed, clutch changed, head changed. Clutch basket removeable without splitting the cases. The head was reworked to match the new 69.5mm bore. The valves increased in size to compete with the GS1000's. The transmission change is a strange one - the early transmissions seem better to me - less clunky.

There are some interesting differences within these 4 main version. The 79 1000 LTD engine is a little odd with a variant of the crank that's unique to that bike. 1973 Z1 engines have a considerable number of difference as refinements hit the bike during the production run. Vacuum take-offs directly in the cylinder head, no center o-ring around the cam chain tunnel, hollow cams and more.

Jeff.Saunders wrote:

Depending how you view the Z1/KZ900/KZ1000 engine there are 4 main variants of the engines (and a few additional variants).

Actually there are 5 if you include the GPz1100 as a "Variation".

wow, Thanks for the tutorial guys! It is really neat learning all this stuff about my bike. And I will say that my 1000 does have quite a clunky tranny, I don't mind though...makes me feel like I'm sitting on a tank.

Well... If you throw in all the variants, add the Japanese market Z2/z750 that's a sleeved, de-stroked version of the Z1 and KZ1000. Add the variants for the 1100's - the bath-tub head, the 18mm piston pins. Then the shaft drive variants, the EFI variants, the black painted versus aluminum engines... it does become a fairly length list. There was even a snowmobile engine based on the kz1000.

Z1 - so the original Z1 had a lighter crank with the lighter flywheels, how would that affect performance compared to the heavier flywheels? I am guessing the heavier ones will carry a broader torque curve whereas the 900 would seem spritelier but youd need to keep the revs up. is that right?

Jeff.Saunders wrote:

KZ1000 (79-80) - aka Mk II - beefed up center section on the crank using 16 teeth on the center section. intermediate weight crank - roughly halfway between the Z1 and early KZ1000 cranks. The cases were beefed up again in 80. 1980 is generally considered the strongest of the engines - and the most sought after for racing / high-performance engines. In the USA, the 79 was the first year of the engines to have smog ports on the head. The stator design changed.

COOL!! Nice to know!
And thanks Jeff. My brake pads and Z1 shirt got here in two days. So I'm all good to go now.
I almost can't wait to burn this motor out so I can build it bigger and badder.
:evil:

9am53 wrote:

Z1 - so the original Z1 had a lighter crank with the lighter flywheels, how would that affect performance compared to the heavier flywheels? I am guessing the heavier ones will carry a broader torque curve whereas the 900 would seem spritelier but youd need to keep the revs up. is that right?

Yes, the Z1 engines rev very quick, but lack the torque of the 1000's. It's not that they are better or worse, each has advantages and disadvantages.

If you are drag racing, there's two distinct camps - those who want torque off the line, and those who want the revs at top-end...

there are no stupid questions......but there are close to stupid questions.....i bet

but this isnt one....


trianglelaguna wrote:

there are no stupid questions......but there are close to stupid questions.....i bet

Jeff might know the answer to this. But wasn't Harley's Federal Trade Commission suit on the Japanese manufacturers' practice of dumping part of the engine size change? I think it was about that time. The 998cc put the bike under the 1000cc limit and thus avoided a tariff.

Bill

i thought that was a tariff on 701cc or bigger leading to all the 700cc bikes that period...interceptor/magna 700....suzuki gs 700...maxim 700 and the kz700 were some i believe...did they also come under 1000cc too??? and wasnt ama superbikes a 1025 cc limit and not a 1000cc class as stated before????billz wrote:

Jeff might know the answer to this. But wasn't Harley's Federal Trade Commission suit on the Japanese manufacturers' practice of dumping part of the engine size change? I think it was about that time. The 998cc put the bike under the 1000cc limit and thus avoided a tariff.

Bill

Jeff.Saunders wrote:

9am53 wrote:

Z1 - so the original Z1 had a lighter crank with the lighter flywheels, how would that affect performance compared to the heavier flywheels? I am guessing the heavier ones will carry a broader torque curve whereas the 900 would seem spritelier but youd need to keep the revs up. is that right?

Yes, the Z1 engines rev very quick, but lack the torque of the 1000's. It's not that they are better or worse, each has advantages and disadvantages.

If you are drag racing, there's two distinct camps - those who want torque off the line, and those who want the revs at top-end...

And for the selective few... You would find a MKII Crank and have it turned into a Lightened Supercrank as follows in the photos.