Introduced in 1977, the Kawasaki Z650 (KZ650 in North America) was sometimes known as the “Son of the Z1” — a middleweight version of the mighty 900cc Z, the “King of the Superbikes.” The 652cc inline four packed 64 hp at 8500 rpm, good for a top speed of 126 mph, and Kawasaki was confident enough in their new machine to host its unveiling on the unforgiving salt of Bonneville Speedway. The bods at Cycle World were well impressed:
“Big Z’s Little Brother Packs a 750 Punch in a 500 Package.” –Cycle World, 1977
A year later, after putting 10,000 miles on their KZ650 test mule, the CW crew hadn’t changed their tune. In fact, they were singing the 650’s praises even louder.
“As a check on all this instant enthusiasm we borrowed a stock 650, with the idea that we’d ride it on a daily basis and flog it in the interest of product evaluation and treat it just as we’d treat our own bike, that is, the usual mixture of over-indulgence and neglect, until the odometer read 10,000 miles. Then we’d see just how good the KZ650 is.
Verdict: Good is too weak a word. The KZ650 is great.” –Cycle World, 1978
Enter our new friend Phil Moore of Leicester, UK, whose very first non-moped motorcycle was a Z650 — a bike he still owns 40 years later! Phil also has a history of racing air-cooled twin-shock Kawasakis at the club level. As you might expect, that means a lot of parts and spares have accrued in his workshop — what better way to use them than another build!
“The inspiration behind the build was to use up all the parts I had lying around from many years of building Kawasaki projects…. Originally a friend asked me to source him an engine, so I got him this 1170 flowed Z1000J engine. Once I did, he changed his mind and said he no longer needed it. So I had a spare engine, which formed the heart of this build.”
Yes, that’s right, Phil and his crew of friends and track-day enthusiasts wedged a flowed and ported 1170cc Z1000J engine into the 650 frame, complete with smooth-bore carbs and an Exhaust Craft stainless steel 4:1 system. The rest of the build would be track-focused, emulating Phil’s first Z1000 racebike.
This “Big650” is now running 43mm ZZ-R1100 forks, ZX-6R wheels and swingarm, Öhlins rear shocks, and tons of parts either homemade or courtesy of various Kawasaki superbikes. Phil’s first outing on the machine was a track-day at Cadwell Park, where he says it “performed brilliantly all day,” tracking well and holding lines without drama.
What’s more, you’ll see that it still retains a license plate and high-output LED headlight — so it’s street-legal.
All in all, this is one mean street and track weapon, and we might even see it take on Mount Jaizkibel next year during Wheels & Waves:
“Its future will be mostly as an interesting old-school street racer with the occasional classic bike trackday outings. But it shows that with some careful planning and a bunch of good friends what can be built in a few months. In fact, it may make its hill-climb debut at Punk’s Peak 2024 if I can get an entry.”
Below, we talk to Phil for the full story on this “Big650” Kwaka.
Kawasaki Z650: Builder Interview
• Please tell us a bit about yourself, your history with motorcycles, and your workshop.
I started riding bikes at 16 with a moped but quickly moved on once I passed my test. My second bike was a Z650, which I still own 40 years later.
I have previously raced big air-cooled Kawasakis at club level in Earlystocks series in the UK, which was for standard twin-shock air-cooled machines, so this bike emulates my first Z1000 race bike.
All my builds are done in my home workshop, which is currently over populated with three other projects. My real passion is classic bike trackdays, and we try and do 10 or so days each summer. There are a group of us all with classic and modified track bikes and we all help each other with advice and parts and skills so it’s a good community.
• Tell us about your Bike…
The bike is a Z650 chassis with a tuned 1170cc motor fitted, along with many modern upgrades to the running gear.
The inspiration behind the build was to use up all the parts I had lying around from many years of building Kawasaki projects. I have always thought that the Z650 is a great bike, as I still have the one I bought 40 years ago.
Originally a friend asked me to source him an engine, so I got him this 1170 flowed Z1000J engine. Once I did, he changed his mind and said he no longer needed it. So I had a spare engine, which formed the heart of this build.
The only parts I sourced specifically for the build were the frame and ZX6R swingarm — all other parts came from my stash of spares.
All the engineering work has been completed by my close friends; all of us were trained engineering apprentices, where we all met through our love of bikes. One welded the twin shocks onto the swingarm; the other aligned the forks and fitted the wheels with new spacers.
Once we had the rolling chassis set up to take 350mm Z1000 shocks and ZZR1100 front forks, I then removed the bottom engine mounts for the Z650 and myself and another friend braced the frame and fabricated new engine mounts. (The top and rear needed only minor alterations to take the larger engine.)
Once fitted, I then built a custom loom locating the coils under the seat, and put the rest of the build together.
The most surprising thing about the build is with a full tank of fuel, the weight of the bike is the same as a standard Z650, and the handling is very good.
The bike’s first outing was a Cadwell Park trackday and it performed brilliantly all day.
Its future will be mostly as an interesting old-school street racer with the occasional classic bike trackday outings. But it shows that with some careful planning and a bunch of good friends what can be built in a few months. In fact, it may make its hill-climb debut at Punk’s Peak 2024 if I can get an entry.
• Can you tell us what the bike is like to ride?
The bike is very powerful off the bottom end with the torque kicking in early. You have to take care with the smooth-bore carbs that you feed the power in carefully, but the bike itself is stable. Going through the curves it tracks well and holds a line without any drama, which must be due to the Öhlins shocks and big forks.
Braking is good but maybe an area I will update as the lever travel on is more than I would like, so an upgrade to the master cylinder is on the list of things to improve.
• Is there anyone you’d like to thank?
Andy from A-weld for the ally welding. Gareth for wheel spacers and fork fitment. Paul for frame bracing and welding, and Hooperman for sorting the paintwork. And also the above for always being there to take the mickey!
Full Build Sheet
- Z650 frame, tank, seat, bodywork.
- ZZR1100 43mm forks and yokes.
- ZX6R (1998) wheels and swingarm
- ZXR750 front calipers and 310mm discs.
- ZX12R master cylinder.
- Öhlins (Z1000 350mm ) rear shocks positioned to retain Z650 ride height.
- Dyna S coils and ignition.
- ZX10R switch gear
- ZXR400 tacho and idiot lights
- ZRX1100 front mudguard.
- Homemade custom undertray and battery box.
- ER5 rear light
- Exhaust Craft “Harris” stainless exhaust
- Race Direct ZX7R rearsets
- ZX7R sidestand.
- 33mm smoothbores
- 1170cc z1000j flowed and ported engine.
- Harris clip-on handlebars.
When these bikes were introduced, Kawasaki took about a dozen riders and a few bikes to Daytona and set the FIM world 24-hour record, at 113 mph average, if I recall. I was one of the riders on the 6-person team (including a female) who came out on top. We ran a 130-mph pace around the oval, with pit stops for fuel, tires and chains. I have a foto, too bad can’t post with this comment.
Love hearing this story, Sam! Here’s the photo you sent.
Hola Phil. Excelente tu motocicleta. El motor de la kawasaki 650 fue el mejor de la historia. Saludos Ricardo
Awesome build Phil.
I remember the mags at the time saying this was the first Japanese bike to challenge or exceed the British bikes in handling! They were great bikes and this one is even better.