1975 KZ400 D

So after putting in some tinkering time, I can see that there is going to be ongoing maintenance and repairs to this bike, Might as well start a project thread here.

What I initially thought to be a 74 KZ400 may actually be a '75 KZ400 D. I am no expert here, simply going off what I have found online, if any expert wants to correct me, I'll be glad to accept it.

I am now thinking this is a '75 KZ400D for the following reasons, when comparing the VIN and engine info from KZ400.com I came across this:
www.kz400.com/ModelidentificationFrameset.html
My VIN sticker is labeled as K4-501683 (6 digits, where as the KZ400.com seems to suggest a 5 digit K4-xxxxx is the 1974)
The Engine stamp is K4E041389





My wife and I took the bike out last night (it is her first bike- learning to ride) and after a short jaunt it started idling and running somewhat erratically. More than once when coming to a stop at parking lot speed, either in gear with clutch in use, or in neutral, the engine would die (no real sputter, but acted starved for fuel). After that, I noticed that when riding at 4k RPMs + it was severely erratic- jumping high and dropping low. Seems as though it was a fueling issue to me.

We have only owned this bike a few months now, have put maybe 120 miles on it so far. Prior to its acting up, I had not done any fuel related work to the bike.

We got up this morning and noticed a faint fuel smell coming from the garage, upon inspection, noticed what I'd call maybe an ounce of fuel dripped onto the garage floor. Turns out there were two culprits. First of all, it seems the petcock may not be sealing correctly, as it was in the "off" position, however fuel continued to flow, though somewhat restricted. The bigger issue, was a split fuel line to the left side carb (I had suspected these would need replacing soon).



I figured this was a good of a time as any to jump into the middle of things. I pulled the batter (new), tray, air box, and carbs. I tried without success to finagle the petcock to shut off, it continued to drip once I had the carbs removed. Finally ended up just draining the fuel into a gas can and saving the petcock for later.

Once off, I decided I may as well open up the carbs and have a look. The bike has just under 20k on it, and the last noted service I can find evidence of was 9 years ago.

Not ever having pulled or cleaned motorcycle carbs, I took my time, and took plenty of reference photos along the way, making sure to dismantle one carb at a time, avoiding crossing parts, and allowing for a reference.

In doing this, I now have a couple questions- first of all, the manual indicates that "The float needle and needle seating will wear after lengthy service and should be inspected carefully. Wear usually takes the form of a ridge or groove, which will cause the float needle to seat imperfectly."

There does not seem to be a real measurement of "lengthy service" but upon inspection, I can see what I'd call a "groove" in the tip of the float needle. (Images provided) Can anyone confirm or deny that this should be replaced?



I also noticed, even after cleaning, the starter plunger rod is a bit crusty looking- I hit it with a brass bristle brush, which didin't seem to do much.


I also discovered the "rubber" boots running from the air box to the carb intakes are completely destroyed- cracked, hard, dry rotted. I have looked around on this site and google- seems as though there are some OE and alternative options to remedy this issue.



And finally I discovered (probably as a result of the non OEM handlebars) the throttle lever assembly doesn't actually seat in its retention hole.


The bike was purchased as a "working project" so none of this is much of a surprise. I have another modern EFI bike as the daily rider, this is just something to tinker around with, and have some fun while doing so.

I'll continue to update as things progress.

Welcome to KZR.
Z1 Enterprises dot com carries carb rebuild kits.
Your air box boots will be more difficult to locate.
Either ebay or make your own. How are your carb boots?

It looks like you are taking a solid, logical approach to this.
The symptoms you describe are often caused by fueling problems, and you have identified several of the most common. Look closely at the carb to engine boots (intake manifolds), as they are likely to be as bad as the air box boots. The petcock will need to be dismantled, cleaned and all the rubber bits replaced. Some of the parts for the 400s are getting hard to find, so don't be bashful about searching the site tor discussions of them.

A genuine Kawasaki factory service manual and some JIS screwdrivers will make your journey to happy motorcycling much easier.

Thanks for the info guys- I had a suspicion about the carb boots as well, especially given the condition of the air box boots and everything I have seen online. They actually look to be OK. Thanks for the info on the rebuild kits Nebr_rex. As far as the JIS drivers and manual, I've got both on order. I'd say the screws on the bike are about 50/50, some destroyed, some look like they've never been off- I guess this also serves as an indicator as to what has been worked on (or not) in the past.

For the stubborn screws, this comes in handy. You can take the bits, tap on them so you can get a good bight on them. One or two smacks with a hammer and they come loose.
Steve