'75 KZ400

So I originally wasn't going to post this as a project thread, but it's turning into more work than I anticipated so I thought it'd be nice to have a place to document it all (because why did I ever expect this to be easy?) My first motorcycle, and my first project!




The bike as I bought it. Known problems: the electric start does not function (it made noise when we tried it but does not seem to be engaging the engine. The kickstart works, however, and the bike fired up). The carbs need synching (the PO took them apart and cleaned them, but did not get around to synching them after). The fork seals need replacing, And the airbox is missing (A previous owner down the line put pods on it. But as I live in Seattle, where it rains 9-10 months of the year, I would rather have an airbox). 

The bike also came with a parts bike (a '76 KZ400, so unfortunately the airbox can't be swapped) and two boxes of varies parts (Including the seat and sideplates), plus a Clymer's manual. 





Got the seat put back on. Unfortunately, while we found the hinges in a box, the latch seems to have been lost along the way. I'll have to order one from Z1. The seat-lock at least works with my ignition key. 

Replacing the airbox is a very good idea.  Take a look on eBay to see if they have the one you need.  There are quite a few KZ400 airboxes there.  Ed

Ordered an airbox off Ebay. It was kind of rusty and a bit dented, so I cleaned it up. Managed to removed the stripped screw holding the little door on, and opened it up to find-



Eeewww, it still has an old filter in it. No telling how old that is. I pulled that sucker out, cleaned out the airbox, and popped in a brand new, much cleaner filter. 

Actually installing the airbox took a little time, mostly because the rubber carb-to-airbox boots I ordered were coming from Japan and took some time to find me. The seller didn't put a ZIP code on the package, so USPS spent about a week trying to deliver it to Washington, DC instead of Washington State. 

Once I got them, though, the airbox was relatively easy to pop in!

Good job getting the air box on. Definitely the right move.
My KZ400 came with an air box made from PVC tubing and a lawn mower filter.

ThatGPzGuy wrote: Good job getting the air box on. Definitely the right move.
My KZ400 came with an air box made from PVC tubing and a lawn mower filter.

Hah! Whatever works, I guess??

This one came to me with the pod filters in a cardboard box, and a couple plastic grocery bags stuffed into the carbs to keep dirt out. I was quite glad to finally get rid of the plastic bags. 

Well, the parts bike came in handy. I noticed that the clutch lever on the (good) bike was really spongey, and didn't return fully like it should when released. Pulled the cable from the lever and discovered it was quite badly frayed. The local cycle shop said they'd have to order a replacement, and quoted me $50. Fortunately, the parts bike still had it's clutch cable, so we pulled that off instead and swapped it over to the good bike. 

  (I can't for the life of me get the video to embed, so here's a link instead)

Now the bike will go into gear! Managed to start it and go a short distance (sorry for how dirty my camera lens is). 

Unfortunately, it sort of went downhill from there. 

One of the things I wasn't expecting with this project was how hard it'd be to find a battery. The bike came with one that didn't fit (too tall, seat wouldn't close over it), we turned that back in for the core fee and tried a couple more, all the wrong size in one dimension or another. Finally, armed with measurements of the bike's battery tray, I tried two auto parts stores, the local cycle shop, and eventually found something of the right size at Batteries + Bulbs. 


After taking the video (we started the bike using the battery out of my friend's Ninja 250 for the video), we popped in the new, fully charged battery and could not get the bike to start again. 

Looking around the bike for the culprit and discovered that the sparkplug in the left cylinder is rather.  .. wiggly. Some previous owner stripped the threads on the hole. Awesome. Time to get a thread tap and some thread inserts. 

After that discovery, gas started pouring out of the right carb, both through it's drain hose and into the airbox. Whether it's due to some problem inside the carb or if we just flooded it via repeated failed attempts to kickstart the bike, I dunno yet. We'll see after it all dries out. 

I never trust PO's on carbs or anything else. Just because they say they cleaned them doesn't mean they did it right or put them together properly. It's common for non-running bikes being sold to say, "the carbs need cleaning".
Take them out, take them apart and check every jet and orifice. Check the valves too...

ThatGPzGuy wrote: I never trust PO's on carbs or anything else. Just because they say they cleaned them doesn't mean they did it right or put them together properly. It's common for non-running bikes being sold to say, "the carbs need cleaning"......

Exactly!  I'm sure the guy selling the bike pictured below said it was running great when he parked it.  Of course he failed to mention that he parked it in 1947!  Ed

The most dubious words on Craigslist: "Ran well when parked."



Well, I bought a tap and some thread inserts for sparkplug hole repair. Managed to get the tap all the way in (after some serious effort), but after pulling it back out it didn't actually seem to have cut use-able threads behind it. So the thread inserts just pull back out because they have nothing to thread into and now I'm not sure what to do.  . .. 

It depends how much you want to do to the bike. I would recommend finding a used head at a swap meet or on ebay; that will probably be the least expensive option.

If you can find a parts bike nearby, that might not be a bad idea.

Edit: NM, you said you have a parts bike.

Yeah, that's probably what I'll end up doing at this point, swapping the head off the parts bike. I was hoping to get this fixed without having to open up the engine (as I am working outside in a backyard) but I might not have a choice.

Well, going back at looking things over with a fresh set of eyes helped. I ran the tap back in and out again, and then tried a different thread insert and it actually threaded in and seemed inclined to stay put! I put the sparkplug into the thread insert, added some high-temp sealant, and threaded that sucker down into the hole. Hopefully, it won't shoot back out of the engine when next I start it.

With the sparkplug problem resolved (*crosses fingers*) it was time to pull the carbs off to see why the right one flooded.





I see that the main jet plates have been replaced with springs, though I have no idea if that'd actually affect the operation any.



taking some of the bits out to have a look at them.

The bike came with a rebuild kit for one carb, so I guess I need to order another. Although, I'm noticing that the jets offered in the rebuild kits don't match the jet numbers listed in the KZ400 service manual I have.

The other problem I noticed is that the petcock dribbles fuel at a fair rate even when in the off position. Pulled the hoses off to get the carbs off and got gas everywhere for a minute before finding a container to drain the tank into. Must be time for a petcock rebuild kit too :Y