Why are there two kz1000 motors?

I have an '82 kz1000 LTD, so from what I have gathered I have a "J" motor with 998 cc's. The older ones have 1015 cc's I believe. Was this a move to lower insurance costs? why are there 2 engines? I presume the larger disp. ones have more power right? Thanks

Just the opposite...the later 'J' motor makes more horsepower, was redesigned over the 1015 motor, and is the next generation Z motor. Nothing to do with insurance...the later 998 motor was introduced in the 1981 year model...the 1015 and 998 overlapped in that year (1981) with the P model bike having the older style 1015 motor and other model bikes with the 'J' motor.

The J model has a different head that breathes much better, it uses a stronger style cam chain and has a different (improved??) clutch. There are other small differences as well. Even though the displacement went down a bit, the J model is generally prefered from a perfomance standpoint. (THe flaming begins here;-) )APE has a pretty good short descritpion of the major differences -
www.aperaceparts.com/tech/techkz1000.html

THanks, good to know. My insurance company has a engine size cutoff at 1000 cc's, so my 998 cc is concsidered a "small" bike and I get cheaper insurance!

I'm sure there are a hundred different views on the subject, but my personal one is by 1980 the KZ1000 was nowhere near as fast as the competition, but still a better engine, but "better" is not the big sales point. So 1981 they build the J engine which is a few less CCs. I think, but could have memory fade, that AMA superbike of the time limited CCs to 1000 so rather than building a new 1015CC engine they opted for 998. The J was lighter and much,much better running engine than the previous 1015cc. Had some teething problems though and reliability was not great.

The J motor is a mix of evolutionary improvements over the earlier engines, coupled with a few cost-cutting measures. In some ways it's a far better engine, in others not as good. Overall the J is a very good motor (except for the crank twisting issue with some of the first year models).

Kawasaki beat it to death in the police bikes - and ran that J engine from 1981 all the way to 2005... not a bad run for sure.

Drag racers have often blended the two together - preferring the earlier bottom ends, bundled with the later J cylinder head.

TexasKZ wrote:

The J model has a different head that breathes much better, it uses a stronger style cam chain and has a different (improved??) clutch. There are other small differences as well. Even though the displacement went down a bit, the J model is generally prefered from a perfomance standpoint. (THe flaming begins here;-) )APE has a pretty good short descritpion of the major differences -
www.aperaceparts.com/tech/techkz1000.html

faster,betterhe says??? your talking about the woman,i mean bike i love! :laugh:

RonKZ650 wrote:

I'm sure there are a hundred different views on the subject, but my personal one is by 1980 the KZ1000 was nowhere near as fast as the competition, but still a better engine, but "better" is not the big sales point. So 1981 they build the J engine which is a few less CCs. I think, but could have memory fade, that AMA superbike of the time limited CCs to 1000 so rather than building a new 1015CC engine they opted for 998. The J was lighter and much,much better running engine than the previous 1015cc. Had some teething problems though and reliability was not great.

Not a bad assesment

When Zuki introduced their GS1000, the fact of the matter is, it was faster than the KZ. 2mm larger intake valve certainly helped.

J motors, IMO are great motors but they weren't the solid motor the predecessor was.

Kawasaki redesigned a clutch basket that was previously problem free for any street application and made removable without splitting the engine case. In the process, the clutch basket was not as strong.

Their tooling at the factory was worn out and they didn't know it at the time. That led to crankshafts that slipped on the presss pins.

Crankshaft thrust bearings were prone to failure. Even on bone stock motors.

Oil leaks were common.

The cylinder had was redesigned with 1mm larger valves on both sides. Larger port runners that reall didn't flow much more air than a KZ head.

At the time, the factories were all about CV carburetors as the solution to increasing HP & meeting emissions standards. Using those carbs was behind the port redesign.

A J motor is a good motor. The thing of it is though, when you decide to push some HP out of one, the smart bet is to tear the complet engine apart and go from the bottom up addressing each weakness.

Kawasaki said the cranks were all fixed in the 82 model but that was hogwash. They were still failing in the 83 GPz11 motors.

In 83, Suzuki got smart and started welding their cranks! Kaw should have done the same. It would have saved them piles of money in warranty coverage. In 1983, we put cranks in over 20 GPz 1100s. That's not to even mention the rest of the J models we did back then. Falicon was pretty busy doing supercranks for us at the time.

Customers had it made in one respect. They rode the bike for a season and got a free rebuild for the next one! Plus the bonus of only paying a portion of a Falicon Supercrank treatment.

Jeff Saunders has a good analysis of another perspective on these motors...JMO

Larry C

thats why i never run right out and buy something thats new and improved,becuase it seldom is till they spend 5 years figuring it out then they start with another new non improved model! but in the j bikes defense the kz1000 wasnt a big improvement over the ol 900,just a new bunch of leaks and other issues! :laugh: now if youll excuse me im gonna go out and sit in my 1970 chevy dumptruck and listen to my beegees 8 tracks before i come back in and watch lawrence welk!(i love those geritol commercials! :laugh: )screw technology! :woohoo:

THIS is one of the most informative threads ever started on KZR.
Keep up the good work guys. Impressive!

inline4 wrote:

THIS is one of the most informative threads ever started on KZR.
Keep up the good work guys. Impressive!

X2

Well, I am having my 1000J worked on now, and it certainly isn't being as bulletproof as my 550! I haven't found any crankshaft issues though (yet)!