TOPIC:

i have a 73?? z1 903 engine that i would like to put in my 76 kz900 frame. can anybody tell me where to get a rebuild kit? i would like the most hp possible, any ideas? the local dealer told me the new 600's are pushing near 130 hp, could i get this engine around that naturally aspirated? thanks, ryan

Wow... First, the current crop of 600s are not making 130 hp at the rear wheel... perhaps at the crank and even then, that is probably an inflated number. Can a "naturally aspirated" Z1 engine make that kind of power? Well... if you have the money, it is possible but why not buy a current 600cc sport bike? It will cost less to go fast and the newer bike has better suspension (handling) and brakes as well.

A stock Z1 comes with ~65-70 hp at the rear wheel. You will have to bore the engine and install larger and higher compression pistons. The bottom end (crank and clutch basket) will need to be beefed up. You will need cams and port/polish on the head. If you keep the bike streetable that means displacement is limited due to heating issues as sleeves get too thin to dissapate heat. Add in valve work, carbs and pipes, you have a bucket of money tied up.

Will this bike be able to keep up with a current hot rod 600cc? Perhaps at the drag strip but certainly not on the road. You will have to make a lot of frame and suspension mods not to speak of brakes.

Just enjoy your bike for what it is... an older classic that is more comfy and simpler to work on than a current crotch rocket.

I'm sure there are those that will disagree with WG but I have to second his suggestion. You can do everything you want with a Z1...it all depends on how big your bag of money is. You can walk right into a dealership and buy an off-the-floor 9 sec 1/4 mile bike. It will take a rather large bag of money to make a Z into a 9 sec bike. However, there are plenty of dragracers on this forum who could assist you, should you so choose.

Post edited by: Mcdroid, at: 2005/10/18 15:19

wiredgeorge wrote:

Wow... First, the current crop of 600s are not making 130 hp at the rear wheel... perhaps at the crank and even then, that is probably an inflated number. Can a "naturally aspirated" Z1 engine make that kind of power? Well... if you have the money, it is possible but why not buy a current 600cc sport bike? It will cost less to go fast and the newer bike has better suspension (handling) and brakes as well.

A stock Z1 comes with ~65-70 hp at the rear wheel. You will have to bore the engine and install larger and higher compression pistons. The bottom end (crank and clutch basket) will need to be beefed up. You will need cams and port/polish on the head. If you keep the bike streetable that means displacement is limited due to heating issues as sleeves get too thin to dissapate heat. Add in valve work, carbs and pipes, you have a bucket of money tied up.

Will this bike be able to keep up with a current hot rod 600cc? Perhaps at the drag strip but certainly not on the road. You will have to make a lot of frame and suspension mods not to speak of brakes.

Just enjoy your bike for what it is... an older classic that is more comfy and simpler to work on than a current crotch rocket.

George knows what he is talking about and has helpfully illustrated why we should all own not one, but TWO Kawasakis!

Really think about what you want and how serious you are about Z1s and KZs. As previously said, you can buy superquick 600s and 1000s for about $10K or so.

Unless you are really into Z1s and KZs and take great satisfaction in improving these bikes, don't bother.

I've been hot-rodding these Z1s and KZs since 1974, doing serious work on engines, frames, wheels, brakes, etc. But remember, it's a hobby for me that costs a bit of money and time. I can afford modern bikes, but I've not been interested in them, at least not yet.

As I told my son, who like you once expressed an interest in an old Z1 or KZ, go get a 600 sportbike because 1) you are far too busy with your business for such time-consuming hobbies, 2) you are 'really' not interested, deep down, in spending the time and money on these older bikes. My son took my advice and he's very happy with his 2003 Honda CBR600/F4.

Okay, are you 'really' interested in this hobby? How much money do you have to spend? If you are a capable mechanic/painter/fabricator, then you can save lots of money. These old motors can make serious power, but cooling can be a problem for commuter Z1s and KZs even with oil coolers. Second, the frame and suspension will need work in order to handle the serious power you hope to develop. But it can be done and it can fun!

With any project you should look at the amount you want to spend and then look at the best return for that money.

The Z1/KZ engine is better than many of the sportbike engines in one important aspect - they are nearly bulletproof - a very tough engine. Plus it is easy to work on and most performance parts are readily available - everything from 1500cc kits with full race cams to turbo setups and more.

130hp at the rear wheel is a very easy thing to do with the Z1 - but it's down to whether you want a streetable bike or not, and how much you spend.

One of the easiest ways to get the power is a turbo setup - this keeps the bike very rideable, but allows you the flexibility of upping the boost and adding race gas to put in some serious drag strip times - several members have turbo bikes - so they can jump in...

If you opt for conventional carbs, you have to look at pushing the bike to the upper limits of streetability for any serious hp that can keep up with the new generation of large capacity street bikes.

Post edited by: sleepy, at: 2005/10/18 19:02

This is a subject near and dear to my heart.Building up a '75 903 is a great project.A 1015 kit with a little head work, a mild 2or 3x cam and a good 4 into 1 and you will have all the horsepower you will need. Driving on the street with a 9 or 10 second bike is a funeral waiting to happen no matter how good you think you are.You don't need 100 horspower keeping on a winding mountain road but you do need more to fly off it.

I like a bike that I can see to the other side, work on by myself and not to mention the pride in "I built it"or "I restored it" . Any fool can spend money and buy a bilke he can't handle. This site has so many people that can give great advice on parts etc.I bought my Z1 new and still have it inspite of owning others over the last 30 years.

im in the middle of beefing my 73 z1 900 up right now..

look around ur area try an find sumone that drag races these bikes or is in to them. iv gotten a set of 1200cc high comp pistons, kz1000 block, race prep head(ported and everything), drag frame, 3 sets of carbs and a pile of other stuff(can almost build another bike) for free. look around on cycletrade or ur local papers for a newer wrecked bike thats a cheap way up upgrade ur suspension. i got a 86 zx600 for $100 and pick a 01 zx9r swingarm off ebay for $20.

u can always swap a kz,z1r 1000 block and pistons, beef the head up, and run a turbo or spary set up

Just another point of view.
That Z1 73 engine is worth a lot of money.
The bore and sleeves do not lend themselves easily to upgrade. Why not look around for a KZ1000 motor and spend your money there?
Sell your motor to someone that will send it to me in Sydney.
Regardz

haha i seem to have upset you. i just like the way a z1 looks compared to a crotch rocket, im not really into the space shuttle look, although i love to go fast, i know the z1 would never go crazy in the corners like a 600, but my friends have 600's and i like to ride with them and im not one who likes being left in the dust. i do appreciate the advice though, about streetability, i'll have to look into a turbo. and i do have some skills when it comes to restoration, just not on bikes, i took a 67 dodge coronet r/t i got for $550 and replaced the quarter panels and floors and built a nice 440 with ported/polished 915 heads 2" headers with 3 1/2" collectors painted it GoMango Orange and am in the process of doing the wiring harness, by myself (i used this car as my high school senior project, i just graduated last year) so if you guys can gimme advice on how to do this bike right i can do it..
P.S.
how much is my Z1 motor worth?? maybe somebody would be interested in trading me a 1000 engine and some parts. in fact, i have the complete z1 bike minus the side panels, just needs a little work, i may part with most of it, (i want some of the chrome)

bangshift440rt wrote:

P.S.
how much is my Z1 motor worth??

The engine number is the key to the worth - generally the lower numbers are worth more.

Some of the parts on the earlier Z1 engines are unique - things like the head, cam chain tensioner, cylinder block, head nuts, sprocket cover...

What are some of the unique parts worth? Have a look at this auction...
cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll...Item&item=4581540817

Engines under Z1E-04000 have most of the unique parts, engines under Z1E-15000 still have some unique parts, and over Z1E-15000 they start to be very similar to the later engines (although they still are more sought after).

If you are really serious about making big power with the KZ, check us out we have virtually everything you could need.

www.kzzone.com

Jay