The chopper craze is dead long live the Cafe Racer!
Yes, its been happening for years, all manor of machines being converted to Resto-mods and Cafe Racers. In fact I started a CR build using a CB750 about 15 years ago, but I chose a z650 for my latest build and progress has been slow due to so many other commitments. Like all my projects I’ve been actively documenting it and this project is past the planning phase now as I am now getting parts made have had some work done and sourced a number of custom pieces.
The Donor Bike
For this build I chose to use a neglected barn find 1977 z650B1. It features in my book “How to Rebuild and Restore Classic Japanese Motorcycles“. But to save you traveling away its shown here loaded on the ute as we transported it home:
The Project Design
The project is to convert the z650 into a modern Cafe Racer. The word “modern” means its going to have many elements of the classic look but more modern features that should blend right in.
This involves a little more than just using bolt on parts. I want the minimalist look here, no side covers and nothing showing behind the engine, custom swingarm, custom exhaust, frame mods, custom electrics and some special features to the engine. Clean lines, almost a “Factory Look”… but nothing like what the factory put together. Black, Gold and stainless…
I wanted to keep the classic spoke look, so I sourced some Buchanon stainless steel spokes but I’ve gone for a black satin rim and black satin hubs both front and rear. Tyres will be left till last but I like the Metzlers on my other z650. The front spokes are from a z900, the rear is only available for a z650 due to the size of the drum brake. New SKF bearings will help it roll for decades.
Speedo drive – removed and replaced with a spacer machined to fit. Speedometer readings will be either a GPS dash or a sensor on the front sprocket cover. This reduces the visual clutter of extra cables but adds complexity.
While I wanted to keep the original disk, I was going to give it an old school drilling. I need to research more options on suitable disks, a modern wave disk would be nice alternative if I can find one to fit the hub, otherwise I’ve had the disk sandblasted at this stage.
A shortened custom front guard to make it legal and a GPz900R front caliper and special mount will ensure it stops well.
Keeping in line with the classic look of the wheels, I decided that keeping the original forks would be good (and logical). If I want to upgrade later I can try a USD fork system and change the front end.
— picture of old forks and new one in pieces and assembled —
I intend to keep the old school drum, but attach a new custom torque arm to the box section swingarm. For the front, a GPz750 or GPz900R caliper (they are almost identical. For the master cylinder, a GPz900R will work very well as it is designed to stop two calipers and I will retain the single front disk. All fittings will be stainless.
The other reason to use the GPz900R master cylinder is to use the matching Clutch Master cylinder and slave cylinder. Rather than a cable clutch, I’ve designed a hydraulic clutch plate to fit where the manual actuator was. More on this later.
A suitable headlight is still to be located. I was thinking an LED 5 to 6″ headlight might do the trick, slightly smaller than the original 7″. Some custom brackets might be needed also or just Alloy Headlight brackets, I’ve located a number of suppliers in China. All look good.
Instruments and Switchgear
- To keep it low profile, no obvious instrument cluster would be ideal, it has to sit low and be visible just above the headlight shell. Still to be designed and scoped but a GPs Digital Speedo/Tacho could be a solution.
- Switch gear – zx10 2005 left and right blocks in great condition have been obtained.
- Clip-ons. Located on eBay and a perfect fit.
- Clutch and Front Brake master cylinders will be sourced from a GPz900R. I’m in the process of stripping the paint from them and getting ready to re-paint and fit new internals.
- Gold levers – sourced on ebay
- Grips – Black anodised.
- All instruments and switchgear to be black, use gold levers as a single feature.
- Fasteners – SS304
- Top triple clamp – couple of options, get one made or try to fit one from something else or buy something like this: https://www.dimecitycycles.com/billet-aluminum-top-triple-tree-fits-kz900-1000-z1.html
The standard rear suspension is a steel swingarm with dual shock absorbers and bronze bushes. I’ve opted for a box section alloy swingarm from something more modern. I bought a disused swingarm from either a GPz550 or GPz750, the gentlemen who sold it to me was not sure. After some research, the job to fit it should be easy.
— picture of swing arm —
To fit it I will need to have a small spacer machined up and a longer internal sleeve made and then hardchromed. The swingarm has 1mm clearance between the frame which is fine, so the sleeve and spacer each sit 0.5mm proud so they will mate flush with the frame when the bolt is tightened up.
— pictures of shaft, bearings and bits —
The spacer is 25mm O.D. 16mm I.D. and about XXX in length. The sleeve is also the same diameters but about 226mm long. At one end of the swingarm is a 12 mm roller bearing that sits between the two spacers and inside the swingarm are two needle roller bearings that appear to be identical to the GPz900R ones. This should allow me to keep the standard bolt, fit snug and do the part with pretty much off the shelf bits other than custom machining.
The swingarm is designed for a mono-shock, so I have turned it upside down, removed the mounting lugs and then need to get a torque arm lug mounted underneath and then dual shock mounts on top. All this must be done lined to the frame so the pivot bolt must be finished and mounted up before I start on the mounts.
After some research the ZR750 shocks have the 14mm top and 10mm bottom mounts and the additional length at 347mm which should give the bike a good stance while still being very usable on the street.
With a minimal build comes minimal body work, however I want to keep the original tank. For a front guard to keep things legal, I purchased a fibreglass guard for another project over 10 years ago and I need to revisit it to see if its still suitable, otherwise a more modern plastic guard cut down or modified will be used (work in progress).
The seat and tail hump will be a custom creation, I have a hump seat purchased with the front guard over 10 years ago and I am still tempted to use it. I need to make a trial fitup and match it to the loop I intend to install.
The hump will sit over the tail loop shown here:
Because the frame had been butchered, I had no issues cutting off the old hacked mounts and fitting the loop. I might add the loop has a tail/brake and blinks built in.
I need to build a custom harness, since most of the factory items will be replaced with better items. The custom zx10 switchgear wont directly connect to the z650, and the charging system will be replaced with a z900 regulator/rectifier single piece unit. Then there are the changes to blinkers and headlight and a host of other smaller changes.
Mounting the bits will be a challenge as much of the original space where electrical items were mounted is now gone, I need to use the space under the seat and between the top frame rails to hold everything, so that means a custom welded tray under the seat. I was in the hardware store the other day and came across some angle brackets that would be ideal for the bike. All pre-bent with convenient holes to aid MIG welding, so I will use this to neaten the layout of components under the seat.
I plan to use relays to power the coils, parking light, horn and headlight. This will help reduce the wiring harness size and give me clean switched power without glitches in the switching from high current arcs. I will look at a more modern trigger from a later bike like a GPz900R to trigger the coil over plugs (if I can get them small enough). Other wise more conventional coils will be used.
Rather than a 4 into 1 system, I plan to route the 4 single pipes under the engine so I can still get to the filter but merge them into a 4 into 2 under the swingarm and then route them up the middle of the swingarm and out under the seat and tail.
Here is a mock up so far, I need to drop the exhaust down and bring them furthur out the back.
At the moment the engine is in a terrible neglected state. I will be stripping it shortly to determine the state and cleaning it up. Then powder coat satin black. A bore kit if it needs it and maybe some drop in street cams. If I can mimic what my friend Dave Sloan has done with his z650 then EFI with a Megasquirt is the go.
More to come! – pictures to upload.