‘79 Kz650B - Semi-Trackbike Build


Been Around the Block
Hey All,

I’m not sure if this should go in the Race Ready or Streetfighter category so I’m placing it here.

As if I didn’t have enough old Kawasaki projects already, I just picked up a ‘79 Kz650B for not much $$. It was one of those “I can part it out for a profit if nothing else” deals. (Reminder to self: delete eBay and Craigslist apps ASAP!)

It looks a lot rougher than it is. It’s really solid, just not very pretty...or clean. The Kerker has surface rust but only a small flat spot underneath. The motor rotates with the kick lever and has a bit more resistance than my Kz1000 does. The black cylinder block and cam cover makes me wonder is there’s been some nice internal work done. The choke plungers are free and slides move easily with great snap-back. Mice decided to camp out in the battery box but overall not bad a bad purchase.






The B model has spoked wheels and a drum brake but someone in the last 40+ years swapped to cast wheels with dual front brakes and rear disc. The rear M/C mount looks ugly but solid.


I kinda have a plan/direction but it may be a bit fluid in nature at the moment.

First thing is to get the bike running. The carbs will take a bath in the ultrasonic cleaner and receive some new gaskets. I estimate that I really only need a few bits to get the engine running. After that, well…I have a bunch of random odds and ends from 15+ years of “good deals”. Here’s kinda what I’m thinking…I may or may not keep it streetable.



I bought these several years ago. They were fitted to a Zx6E which I thought was a bit odd. The rear does not have a cush drive but the front has provisions for a speedo drive.


Add in a de-bracketed Zr7S swingarm. The swingarm is steel, meaning I have the ability to easily weld on shock mounts. The biggest hurdle will be overcoming the 244mm pivot width. I think I have a plan but it’ll take some measuring and math.



Not shown is a 1995-1997 Zx6R front end. I’ll either have to swap bearings or stems (TBD). The Zx6E wheel shares all the same axle components so the PM wheel should be a 100% bolt-in affair.

TAG handlebar mounts are on their way to hold a Bikemaster Superbike bend handlebar. A set of used Galfer front rotors and a gas cap are coming too. I also have a set of aftermarket Gsxr/Sv rearsets and a Performance Machine 2-piston classic caliper to be mounted for the rear.

This may or may not be a quick build. Depends on time and $$ available.

Later, Doug
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Cool Project. This could be the only KZ650 with Chicanes in existence. 180 is alot of tire for that level of horsepower. I have been in a similar quandary with rear wheel sizes for my 750 track bike... lots of 5.5" or 6" lightweight rear wheels available but really need a 4.5" or 5" for a 160 rear tire. Is it better to have lightweight wheels that have too much tire or heavier wheels with the right wheel/tire size? The other option is to spend a crazy amount for custom lightweight wheels with the correct size. I'm still on the fence personally.

Believe it or not, the rear is a 4.5” with a 160/60 on it! First time I’ve ever seen/heard of a 4.5” Chicane. Not sure if it was a custom built wheel but like I stated before, an odd-ball setup.

Later, Doug
you scored! Rare for sure, and the perfect size for the KZ650. Another benefit is a 4.5" keeps it eligible for most vintage classes if you ever wanted to do any racing. I have been trolling the web hoping to find a lightweight 4.5" wheel used and haven't had any luck yet. I might just break down and order a custom Dymag.
Another benefit is a 4.5" keeps it eligible for most vintage classes if you ever wanted to do any racing.

The PM’s restrict me from AHRMA V5 (I think) along with anything more than 2-piston caliper. I might be allowed in WERA since they seem a bit more lenient.

I may just build it for a couple trackdays a year. That’s why I’m also thinking of keeping it street-legal so I can put some miles on it.

Later, Doug
Ordered up some parts. Grabbed a used gas cap from eBay. Also scored a pair of Galfer wave rotors with the correct diameter of 300mm for $75/shipped!! I found my old Pingel adapter plate so I can mark that off the list, too.





Later, Doug
The bike didn’t come with keys so I thought about having a key made until I found out A) the ignition switch and seat lock were different codes & B) the switch that was installed has a 6-pin connector and no 7th wire because the 79 has an extra wire compared to any other year. So I ordered a complete used matching lock set for a little less than 1/2 of what I paid for the entire bike. Getting two master keys and two copies may not have been much cheaper anyways.

I’ve pretty much decided on using a spare set of ‘76 900 VM26 carbs for several reasons: I have them and I rebuilt them before putting them away, the current carbs need rebuilt plus they have an accelerator pump, and I’ve read the 26’s offer more performance like the 29’s do on the 900/1000s. The last one I’m not so sure about but might as well try.

Later, Doug
I had some time so I pulled the Zx6R front end down from the rafters. Center of axle to top of fork leg is 30”. Stock Kz forks measured 29-1/4” with weight on them. I’m going to lose ground clearance from the swap from a 19” to 17” wheel but hopefully none due to the fork length. I had a stock Kz900 stem that I was going to use on a dead project and compared it to the Zx6 piece. A stem swap is going to be a must. The Kz stem was welded to the lower clamp. The Zx stem is pushed in and held with a retaining ring. Both stems look like they’re 28mm OD. (I know the one pic shows 27.92 but hard to hold a camera and caliper too.)



Later, Doug
dont forget the stock triple has something like 1.5" of drop in it not sure what the zx6r has, but shouldn't be a problem with ride height. I think with the bigger KZs ride height is more of a problem
After more thought, a simple stem swap from the Zx to the Kz stem isn’t going to work as well as I hoped. The Kz’s stem is the same 28mm diameter through the triple clamp but increases to 30mm above. This means I can not push it up through the triple to install it. I thought about turning the bearing journal down to 28mm, but there’s no lip around the bottom to retain. Then I thought some more… welding a bead all the way around and then turning it to machine a lip could work for the bottom. Then my attention turned to the other end of the stem. The Kz and Zx stem are vastly different as well.

Again, I mentally raided my parts inventory and remembered I have a triple clamp set from a Zx6E. I bought it to use on my Gpz750 project about 10 years ago. I compared the two Zx stems and think I have a winner.

Kz…Zx6E…Zx6R. All stems are aligned at the bottom of the lower journal.

The two Zx stems: upper end.

Turning down the 6E’s 30mm lower journal to 28mm. This will match the 6R’s lower clamp’s bore.


I finally ordered a much needed boring head for my mill. I’ll need to to sink the 6E stem a bit further into the R’s clamp since it’s thicker and I need to keep the lower bearings journal location the same.

Later, Doug
This build is pretty cool, but it really won't be AHRMA Vintage Superbike legal. They don't allow USD forks or PM wheels. They also require OEM bodywork and the original gauge housings. They are really going for the period correct appearance.
It will be legal for WERA V5, but the closest WERA races for you would be Grattan, MI or Birmingham, AL although there is talk that they may get a date at Memphis.
it really won't be AHRMA Vintage Superbike legal. They don't allow USD forks or PM wheels. They also require OEM bodywork and the original gauge housings. They are really going for the period correct appearance. It will be legal for WERA

Right. I read the rules for AHRMA and WERA. PM wheels as well as any brake caliper having more than 2 pistons are not allowed in AHRMA.. The ‘95-95 Zx6R forks are RWU meaning that with a rim and caliper swap, I might fit in.

Later, Doug
Right. I read the rules for AHRMA and WERA. PM wheels as well as any brake caliper having more than 2 pistons are not allowed in AHRMA.. The ‘95-95 Zx6R forks are RWU meaning that with a rim and caliper swap, I might fit in.

Later, Doug
Yup, that would work for both organizations. Kawi has some 2 piston brakes that work pretty well, I think they may have been stock on the ZX6E. I don't know if they will mount up to the ZX6R forks without some modification to their mounting points.
I tend to prefer WERA over AHRMA, based on my long history with WERA, but have raced both and don't really have anything against AHRMA. I built an FZ600 which is legal for both, WERA V5 and AHRMA Next Gen Superbike Lightweight.
I also have a bike legal for Vintage Superbike Middleweight and WERA V4. I like to have options.
The FZ has SV650 wheels, brakes and forks while the Seca has CBR600F wheels and FZ600 forks and brakes.


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I received in the matching lock set yesterday and installed both the ignition switch and the seat lock. I got the steering lock and gas cap too. The old Kz caps don’t have tumblers so any key will open them. I guess I have a spare now. I may swap out the steering lock. I will need to machine a slot or hold in the Zx6E stem if I want to use it. So I’m still mulling that over.

Since. I had an switch that worked, I hooked up a spare battery and hit the start button. What do you know….it cranked over! The battery was sort of week, but it worked.


Later, Doug

Let’s see if the link works….

I cleaned and gapped the points, removed the carbs and sprayed some starting fluid in the intake ports and…it lives!

I also filled out all the forms and sent a check to the Vermont DMV yesterday. I’m trying to use their system to register it for street use.

Later, Doug
Why so? I have had several Kz’s and not had problems with the stock non-electronic setups.

Later, Doug
The points would never stay in proper adjustment on my 78 KZ650. It would do fine on a ride but the next time I tried to start it, the points gap would be wrong. I thought it was the screws and replaced them. Then I thought it might be the points plate (OEM) and replaced it. I finally asked a Kawasaki tech at a WERA race. He told me had had seen the same problem on 650s and advised using an electronic ignition. I did and never had another problem. I worked on another 78 about five years ago and it had the same issue.
I should have been doing other tasks in the garage but couldn’t help it as I’ve not machined anything in a bit. I was having chip withdrawal.

I machined my top clamp to remove the ignition switch lugs and add holes in for my bar risers.












Later, Doug
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