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Kawasaki Z400 - cafe racer build

6734 Views 10 Replies 7 Participants Last post by  CAPTAIN AWESOME
A bit about me. a moment when clarity of thought was clearly absent; I challenged a long-standing friend to build a café racer. We're both in our 50s, have been riding forever and would rather be in the garage than with the wife learning new skills and creating something (not quite true; but you get the idea!). Just in case she ever sees this; I'm only joking Darling. REALLY! In any case; if she ever went on this forum; then that would raise serious questions. I've taken apart and re-built saxophones in the past; but am struggling to find any cross-over skills (although I suspect that my ability to find tiny screws on the floor after I've dropped them will come in useful)

So I've now got a decent 1977 Z400 (UK model). It's a great runner and mechanically ok; so the main area of work will be creating 'the look' and trying to eek a little more performance out of it. The reason for choosing the Z400 was because I had one in the 1980s. Not the most sensible of reasons for choosing this as the base bike; but the heart can often be stronger than the head and we have little say in our choices (back to the wife again).

I'm glad that I've taken the time to read various posts and articles and haven't fallen into the trap of just stripping it all down, chopping it up and then thinking what to do. I've got a pretty clear vision of what I want and will post some photos and sketches in due course. This is going to be a long project as I am in no need to rush, want to get it right and am a patient chap.

I have a little bit of technical know-how; but not much and a couple of issues spring to mind. I really want to open up the middle of the bike and remove the panels covering he air-box and replace this with cone filters (I assume that K&N are the best?). This immediately raises some questions. Can this be done (It would appear so from the images of other Z400s that I've seen); but I've read that it shouldn't be done. If it can be done; how do I know which cones to put on and what would I do with the pipe that is the crankcase ventilation system?

We all have to start somewhere and any help would be appreciated.

I wonder now if I'm going to get a load of abuse (the wife theme keeps returning"!).

Cheers for now.

Big Sax
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welcome to the forum.. that is saying alot to me, your ability in rebuilding saxaphones ..
and that you havent as yet torn the kawa apart in haste..

first take lots of pictures, they are your friend as you can refer to them when putting it back together later on..
find the factory service manual and if at all possible (and its not in the service manual) the assembly guide the techs use when they first assembled this

as to pods.....
read the threads concerning their use,especially find info on what your particular model may run best with in reguards to jetting, shimming and needle settings required.. top of the line pods can be made to work well , yet will affect your driveability in daily street useage.. pods are prob best left for true race bikes as the carb is set up for running in a much narrower power band requirement.

know that your going to experimenting with jets, needle's and shims until you find the overall sweet spot .

the pipe .. it is there to channel unburnt gasses back into the combustion process that the rings did not seal against during compression. this pipe also enables moisture to escape ( be burnt) that the oil would otherwise have to suspend in-between changes ... its good to have some sort of vent as reburning makes it more enviromentaly clean and getting condensation and contaminents out of the case is better for the engine itself..( rust and corrosion internally)
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Welcome..... Where abouts in London are you?
Welcome..... Where abouts in London are you?
I work in Covent Garden and live in Shepperton. A great daily commute on the bike.
Thanks for taking the time to reply.

The camera is ready; as is the notebook. I've just orderted a Haynes manual; so that should help and I'll look out for the assembly guide. Good advice; so thanks for that.

I think that I understand the bit about the vent and I'll maintain the pipe to allow the gases to escape.

I'll get some pics and upload them to the forum.

Cheers for now.
I would once again promote my form follows function message to the great unwashed out there. My advice at this point is for you to leave the carb and airbox alone for now. At this point you should concern yourself with other items such as tires, brakes, suspension and the handlebar to seat to feet relationship. You may want to consider what you will do with the exhaust system as it may be affected by the footpeg location. Once you get all of those pieces dialed in you will be ready to decide what to do with the aircleaner situation. That is probably 6 or 7 steps down the road from where you are currently at. Get it running and stopping and handling.
You are going to have so much fun with the build...
perhaps i can provide some insights about the KZ400 and "cafe"ing it, as i am in the finishing stages of building one.

Brakes - the front caliper will provide good braking, but you should consider replacing the brake line to a braided one, also consider replacing the master cylinder.
i have mine set up with a 14mm MC and a stainless steel braided line, new brake pads - it is great, don't need to squeeze the lever, two fingers on the brake lever provides more than adequate braking power.

Rear suspensions - look into some HAGONs or some thing like that, i replaced mine with a set of HAGONs and the ride improved dramatically, it feels much better when cornering.
Front suspension - replace the old springs with progressive springs (look for 11-1109, amazon have a good pricing on these), i got these on my bike along with front fork oil replacement and i can truly say that now, with the combination of the rear suspension, the bike handles fantastic, cornering in low speeds feels so safe that you actually looking into leaning the bike even further.
and high speeds (if you can get there on a stock KZ400 :) ) turns, pure fun... no front nor rear wobbling, no unexpected movements, the bike gives you a very comfortable feeling that makes you want to go back and take the turn again, leaning id down.

Rearsets - i built mine from scratch, moving the pegs location approx 25cm to the back, along with a lower clip-on handlebars, it is much more comfortable to ride, the seating position feels more natural.

bearings - if possible, try to replace all of them, front and rear wheel bearings, swingarm bearings, tapered steering bearings (you can get the "all balls" set, look into 22-1012, these fits perfectly).

engine - if you are good with your hands, you can port and polish the heads, should provide a few more ponies out of this engine.
also, look into a bigger bore, i just got a set of 67.5mm pistons and rings and going to bore my (almost new) engine to 440cc... as the 400 is a bit on the weak and slow side... the 400 will run out of steam at approx 130-135kph.

Pods and carbs - if you have access to other carbs, try it... pods and carbs is all a matter of trial and error, if you have enough time and patience , you should get it running properly.
i got a set of carbs out of a Kawasaki ER-5 (Keihing CVK), re-jetted them and got it to run with an oiled pods (on a short, 6cm extension) mounted onto the carbs. still needs a bit of a tweaking, but it can be made to run.

when you're done with all of that, it is time to start thinking about seat, paint, lights (flawless electric system is a must, IMHO) and other stuff you like to have (or dont have) on your bike.

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Thanks Ravios. That's great advice and reinforces the notion that time needs to be taken to consider everything properly and not just dive in with half-baked ideas. I'd love to see some images of your KZ400. Cheers.

Big Sax
Most everything has been covered so far, but for technical info check here:

There are workshop manuals for each model as well as specific maintenance information. There is also the kz400 twins forum, but it's pretty baron these days.


If yours is a 77, you probably have the earlier head design with internal top end oiling. The earlier models had oil leakage top end problems so they later switched it up to external oiling. If you happen to stumble upon a 440 motor in good shape, snatch it up and toss it in your frame. It's a 6 speed and the extra cc is another benefit to the upgrade. The only downside is the majority of the 440 bikes don't have a kickstarter. There are some out there, and it could be converted, but probably not worth the cost. Also look into a factory 2-1 exhaust. You can swap out the muffler rather easily as well.
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