Dual plugging J heads

I half suspected that...the entire motor is supposedly different; after all it's a plain bearing crank-shaft motor, and if I designed a motor it would be from the crank up. Just a thought.
-KR

No one ever put a Zeph head on a KZ, so I knew there had to be a reason.

Just a question Jay. I have heard that the zr1100 engine is based on the voyager 1200 and that there is not much you can do to mod these engines very much. The kz motor remains the platform because there are so many more possibilities and the engine is much stronger than the zep. Is it just because of the bearings used on the crank of the zep that make them weaker? Does the dual plug head work better? I had a zep until it burned up in the fire I had in my garage. I liked the way it ran but in no way do I feel that the bike could take my ltd although the geometry and everything was different my z pulls just as hard and is probably just as fast. Although now I will never be able to compare.APE Jay wrote:

No one ever put a Zeph head on a KZ, so I knew there had to be a reason.

The deal with the Zeph was that Kawasaki was working closley with the late Dave Schultz pro stock program, and decided to build a bike with some of the pro stock tricks. The head, etc.

However, they way over priced it and it didn't sell. Too bad.

As for the crank, all high horsepower engines run plain bearing cranks. Busa make up to 700 hp ( dyno shootout queens). The roller bearing crank was the weak point on the KZ motor in top fuel and a plain bearing lower end had to be made for them so they could evolve into what they are today.

The Zeph would have been a logical steping stone fron the KZ if it had sold.

Jay

i know 2 guy's that bought them and thought they were great bikes typical o.e manufacter mentality thou build a bike that was cababile of decent horsepower and then the kiss of death tuned for mid range why do they always do that with potential muscle bikes, guy's that buy these bikes want the power of a sport bike with out the body work and riding position, that is one of the main reasons we are all into building 30+ year old bikes we want the power and handling with out the look and feel of the sport bike. i was very interested in the zrx1100 when it came out but i backed off when i found out it was basicly a casterated version of what i was already riding the better suspension that i would get was not worth the extra price i would have to pay. any time they have given a standard, superbike type horsepower they make it so ugly no will buy it [suzuki b-king]. kawasaki are you reading this.

Reading through some old posts has me thinking. I noticed that a Zephyr 1100 has 73.5 mm pistons and is a two valve motor. I can't find anywhere that the wrist pin size is mentioned.

I am curious, since 73.5 is the same as second oversize KZ1100 piston, maybe the pistons would fit the old bikes yielding 1120 cc with standard 66 mm stroke. Ron Ayers also lists OS pistons at 74 mm and 74.5 mm. I don't know if they are still available though. They would yield 1135 and 1150 cc respectively I think.

Questions would be - what size wrist pin, and what is the height of the piston from the wrist pin to the top of the piston.

I got the Zephyr bore size from here and then checked it against some other sites.
www.fixya.com/motorcycles/p983823-kawasaki_zephyr_1100_1992

Anyone have a Zephyr 1100 piston that they could check?

Take care in swapping Zephyr parts. Although I suppose it is entirely possible (the Zephyr motor is a two-valve like the KZs) but it's a plain-berring crank-shaft and I doubt that there are any swapping motor parts. But I have heard crazier things. If you discover something interesting about Zeph/KZ motor swappings, please DO share!


-KR

Jay thanks for the info a little late. But your answer makes me wonder... Why then does everyone say that there is not much you can do to build them? I really loved my bike. Second gear was weak though. I broke it and noticed that many of the people who I knew had that problem too.
I was deeply saddened when I saw it go up in flames but happy later because I resurrected my 79 and later got an 80. The genuine articles. Well, it would be a good thing if they brought back the zep and do the bike right so that it has the potential to own.
APE Jay wrote:

The deal with the Zeph was that Kawasaki was working closley with the late Dave Schultz pro stock program, and decided to build a bike with some of the pro stock tricks. The head, etc.

However, they way over priced it and it didn't sell. Too bad.

As for the crank, all high horsepower engines run plain bearing cranks. Busa make up to 700 hp ( dyno shootout queens). The roller bearing crank was the weak point on the KZ motor in top fuel and a plain bearing lower end had to be made for them so they could evolve into what they are today.

The Zeph would have been a logical steping stone fron the KZ if it had sold.

Jay

kpier998 wrote:

Reading through some old posts has me thinking. I noticed that a Zephyr 1100 has 73.5 mm pistons and is a two valve motor. I can't find anywhere that the wrist pin size is mentioned.

I am curious, since 73.5 is the same as second oversize KZ1100 piston, maybe the pistons would fit the old bikes yielding 1120 cc with standard 66 mm stroke. Ron Ayers also lists OS pistons at 74 mm and 74.5 mm. I don't know if they are still available though. They would yield 1135 and 1150 cc respectively I think.

Questions would be - what size wrist pin, and what is the height of the piston from the wrist pin to the top of the piston.

I got the Zephyr bore size from here and then checked it against some other sites.
www.fixya.com/motorcycles/p983823-kawasaki_zephyr_1100_1992

Anyone have a Zephyr 1100 piston that they could check?

Well, I bought a set of used Zephyr 1100 Pistons on the chance that they would be usable and give me 1120 CC. Here are some pictures with the 1089 piston on the left and the Zephyr piston on the right:

Another view:

And a top view:

The Zeph piston is kind of a crowned/flat top hybrid. The crown is much taller at the edges, but then it is chopped off.

It appears to me that compression would be significantly higher if run in a KZ J motor. However, for me, there is a problem - the wrist pins are not 17 mm. I will check the size, but I believe they are 18 mm like the 83-84 GPZ.

So, it was a good idea and worth a try, but I will have to hang on to them till I have a 83/84 motor, or sell them on feebay.

Other items of interest. The piston skirt stops just below the boss of the wrist pin on the Zeph piston. The skirt area is significantly smaller, and in general, they look, to be made to be much lighter. If I can find some small scales, I will weigh each of them and post the weights.