1976 KZ400, coming soon to a dirt track near you

Parkwood60

Active Member
EDIT: I had originally linked to pictures on my Google+ account, but a change in jobs lost me that Gmail address, and + account. So some image links are lost to time, but I tried to fix the others.

No much to look at at the moment, and lots of confusion as to what year the bike actually is, but I figured I ought to start a thread. I believe the bike is a 1976 KZ400, or at the latest a 1977. The title does say 1978, but it must have been a left over. Picked this up from behind a house where it had sat, with just 12k miles on it, since 1989. Here's what it looked like when I got it.

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The motor was stuck but it was nearly all there and it did have low mileage. Plus it was a classically styled, 360 degree twin, so why not make a flat track bike out of it? Time is tight and I still haven't really finished my 1972 CB750 Cafe Racer, but I wanted to have this together and running for the Hell on Wheels flat track event in August of this year. Could I make that happen?

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Washed and stripped of the touring gear it didn't even look half bad. You can't fake this kind of patina (after washing and rubbing compound).

So I just sanded it with some fine grit wet/dry paper and cleared over it.

I did manage to unstick the motor with generous application of PB Blaster and transmission fluid, then rocking the bike forward and back in gear. But I had to take the top end apart anyway.

More to come tomorrow until I am caught up.
 
Here is the event I am shooting for, come on out if you are in southern california:

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https://www.facebook.com/events/523457591113372/
 
It looks pretty good for sitting out that long. If that is the early engine design (head gasket looks like a smiley face) start looking for a head gasket or gasket set. They are not the easiest to come by if you need it in a hurry. Also there are two oval orings that go between the head and cylinder. Start looking for an oem set of those.

If you have the parts they are pretty easy to work on.
 
Powderfinger said:
It looks pretty good for sitting out that long. If that is the early engine design (head gasket looks like a smiley face) start looking for a head gasket or gasket set. They are not the easiest to come by if you need it in a hurry. Also there are two oval orings that go between the head and cylinder. Start looking for an oem set of those.

If you have the parts they are pretty easy to work on.

Getting ahead of the build here, but I did already get the gasket set, and oval o-rings. Piston rings too. I had unstuck the gummed up original rings, but broke an oil control ring trying to get them back into the stupid taper at the bottom of the bore. Cruising Image, out of Japan via eBay had the gaskets. The o-rings were just some random eBay seller.
 
Spent most of yesterday making 2 stupid flat aluminum adapters so I can remount the stock carbs using Kawasaki KZ1000 police bike intake boots. It really wasn't all that hard, but the chuck on my drill press is messed up. Its got a wobble, and it won't close to smaller than 1/4". That plus the cheap Harbor Freight hole saws made it much more difficult than it should have been.

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Cop bike intakes are obviously about 1/4" shorter than the correct ones. No big deal, if that was the only issue I would have just run them as is. But the ear holes to mount it are about 6mm narrower, without a lot of meat to drill. Plus the stock intakes mounts are offset to one side (lets say the bottom, but its diagonal), and the mating surface at the head is really minimal, so there isn't much room for changing that.

Sadly, online images lost

Here you can see the outline of (right to left) the new boot, the original boot, and the 2 superimposed on the same center port opening.

Drill baby, drill. In hindsight It obviously would have been better to leave 2 sides square until I finished the parts that required viceing.

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Here you can see how little there is of a mating surface on the head. The hole in my spacer is a little bigger than the intake port, and a lot bigger than the original hole in the boot. But it is exactly the same size as the hole in the new boot. I actually expect to pick up a few HP in the top end because of this.

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Drill and tap holes in spacer to mount new boot to. This actually worked out great because the offset, and width of the mounting holes on the head allowed me to fit the new boots between the allen head screws, without any countersinking or anything.

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Of course the second one I made took me practically no time at all, once I had made the first one. The beauty of these BTW is that the boots for KZ1000 police bikes are cheap and available, and can also be used to mount aftermarket round slides eventually. I may take one of these and send it out to a local CNC guy to have reproduced for sale. I know there are plenty of KZ400 and KZ440 bikes out there, and almost no intake boots. Of course if the CNC guy made them they would look better, and I'd shrink the hole in the spacer down to the size of the intake port in the head. It would still be bigger than the factory bottle neck.
 
And because I know you all like pretty things, and not just greasy motor stuff, here's how I spent the rest of my day.

The stock grab rail behind the seat was sized for a 4" thick seat, and I'm going to one closer to the popular ironing board look.

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But since this is a cheap and fast build I am using the stock pan, and not welding in a frame hoop, or making a kicked up rear seat pan. Besides, this pan is plastic, and there would be no weight savings to be had by getting rid of it in favor of a hunk of wood, or aluminum.

So I got the thickness of the padding settled on the seat so could see how it was gonna look.

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The cover will compress it even more, but I haven't made it yet. Then I took the grab rail off, sliced 3" out of it on each side, and welded it back together. It took a little tweaking with a big pipe to make it about 1/2" wider afterward to meet the frame mounting tabs.

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You may also notice the fender mounting bolts: 12mm diameter bolts and nylock nuts from Home Depot, which replace the original turn signals. Then rifle drilled because 12mm is way, way beefier than a little plastic fender needs.

I also picked up the ubiquitous eBay twin round LED tailight/brake light/turn signal/license plate mount. Sure I could just drill 2 holes in the fender and be done with it, but I am going to weld 2 tabs to the grab rail instead. In the end its just going to be more secure.

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This will be running and ridable next weekend. The actual event is the weekend after that, and I would like at least a few laps of the cul de sac before loading it up in the truck.
 
I realize I'm way behind here. I also sourced a new master cylinder in the 11mm bore size that is suppose to give these old 1 big piston calipers much better feel. Then I took off the stock chrome front fender and mounted a cut down universal plastic vintage dirt bike fender to fit.

Before:

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After:

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Kawasaki made it easy by mounting the original front chrome fender to a steel brake with 6mm chrome acorn nuts, which I reused, along with the fender mount/brace.

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The rear is the matching universal MX fender as well. Since the stock KZ400 inner fender was already lightweight plastic, I kept it, and just mounted the dirt bike fender to the rear of it.

I went with yellow on the fenders because 1) The blue ones are hard to find 2) the blue ones are lighter colored than the tank, but darker than the pin stripe. The yellow is close enough to the stripe color that I don't mind it. I did buy a pair of blue number plates, but they have not arrived yet.
 
Not a ton of work today. I mocked up the cylinder head, but didn't torque it yet, so I could check out where the header pipes were running, and figure out what end I wanted to put on them.

I did however get the number plates, and fitted one side. The other side will fit, but first I need to move the reg/rec a little and mount a battery.

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Saturday was a low point in this build. Everything I tried to do was just going sideways, and I didn't get hardly anything done. Well, that's not really true. I got the tires mounted, put on the "new" shocks, and buttoned up the motor. But I wanted to get a lot more done.

The biggest pain in the ass was the front brake. Everything was stuck and gelled from sitting. So I was planning on swapping on an ATK dirt bike master cylinder with 11mm piston, and maybe braided lines. The first problem was that no amount of effort was going to get the original hard brake line out of the brake caliper. The second problem was that the caliper piston was stuck in the caliper. And the 3rd problem was that the dirt bike master cylinder was just as gellified as the original KZ piece, and the piston wouldn't come out.

Anyway after wasting hours on it Saturday I just let is soak in PB Blaster, and Sunday I managed to get it. The hard line is still stuck, but the caliper and master cylinder work once again.

I took no pictures, it was pretty disgusting.
 
Sunday was a better day. New fork seals, new headlight ears, exhaust nearly done, wheels back on it, carbs back on it, etc. Its still not running, but after the amount of gunk I took out of the carburetors I am confident it will be tomorrow.

I used a flat plate with a pipe in the middle, and two 25lb weights to figure out the spring rates of all the spare parts I had around. Turns out the Taiwan eBay $99 Progressive knock off shocks have a 110lb spring. I used those shocks, with a much lighter 90lb spring on a Honda MT125 dirt bike I have, so I had the springs around. They fit almost perfectly on an old set of Mullhollond shocks I had (which must have been off an 80cc bike, they had 80lb springs on them). I made a preload collar out of PVC pipe from the hardware store, and BAM! We've got damping, and about 1" more rear ride height, 1 degree less rake.

Fork Gators are by 4 Wheel Parts. They are meant for big off road truck shocks, but they fit fine. I cut 4 folds off the bottom of them, then just fit it around the bottom of the fork. At the top I put a little glue on the top edge, then slid a wire tie under it to hold it up against the triple clamps. These gators are $6.99 a pair, and I'm pretty sure they are made out of a nearly indestructible synthetic rubber. They seal so well I had to poke a few small holes in them to keep them to let air in and out so they wouldn't suck closed on extension.

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The exhaust isn't quite finished (and the seat is only just started) but its the stock head pipes with a "cheese grater" baffle slipped over it, tack welded, and a 9" turn down tacked to that.

Cheese grater
http://www.ebay.com/itm/NEW-1-5-EXHAUST-BAFFLE-SILENCER-4-LONG-TRIMUPH-BONNEVILLE-TIGER-BSA-LIGHTNING-/251892617147?hash=item3aa5f84fbb

Turn down
http://www.ebay.com/itm/1-50-Turndown-chrome-exhaust-tips-1-1-2-I-D-2-pcs-JTD112-2-ITD112-2-/261832099810?hash=item3cf668c7e2

Maybe more updates later, but definitely tomorrow
 
Got a better picture today over lunch. I finished the exhaust (including plumbers tape hanger for the back). Mounted the brakes back up. Removed the center stand... Only about a million other stupid little things to do.
 
finally, FINALLY got it to run today. Yesterday when I finally had it all buttoned up I had no spark. Today I troubleshooted a little, determined the coil was bad and swapped on a CB750 one I had around. Pretty much the exact same coil, just turned on its side.

https://www.youtube.com/watch?v=lMCnHzDFAxI

BTW - I would guess the "baffles" I put in the turn down tips do just about nothing to cut down the noise. Not sure I can ride it on the street this loud with a clear conscience.
 
Looking good. Sounds pretty mean. Are those Duro308 tires? I got a 78' kz750 twin in shed that I think going to end up similar to this.
 
Yes it's a Duro H308 18 x 3.50 on the front & 18 x 4.00 on the rear. They look good, not how they will do on the track, but they are a knock off of an old Pirelli tire that guys flat tracked with back in the day.

Not sure if I can shoot video of the race tonight, but we shall see.
 
Soooooo, long story short, I missed the race. The bike was running, but not too well, and the steering stem bearings were scary notchy when riding it around the neighborhood. I'm going to try to make it to an opened practice session next month. I did see a Harley Sportster based tracker at the race that won its race with the same Duro tires on it, so they seem to work pretty well.

Here is how she looks "complete" now that that seat is on and its buttoned up (though there is still a bit of a mess of wiring under the seat). The nice thing about those number plates is that they hang on the stock side cover tabs, and if you put the side covers back on it they hide the foam filter mod I did to the stock air box.

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Long story short, I got laid off, the bike sat in the garage for 6 months gathering dust, the Google Plus account I had the old picture hosted on was attached to my old job, so there are some broken images in this thread. I tried to go back and rebuild with images hosted on my own wordpress blog, but I really don't feel like trying to upload all the pictures again, just for the sake of this thread.

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The bike is done, and I'm on to the next project, a Honda CM400T Bosozoku bike.

Here's a link to my blog post about this KZ400 with a bunch more pictures.

http://piledriverz.com/2015/04/05/1356/
 
I haven't, but I'm sure it would do okay on a dirt trail. I would be concerned about the garbage damping on the rear shocks and lack of any real seat padding. It also has an 18" wheel on the front, which will effect its behavior rolling over obstacles.

I have a Honda cl450 that I have done plenty of off road riding on including the Elsinore gran prix
 
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