February 21, 2015 Henrique "EGG" Costa

How to build a great cafe racer

Everybody that is thinking about building his own cafe racer is imperative some study and knowledge. So as I’m trying to put together my first I’m compiled some of the best post I could find on the matter. Most came out from Bike Exif. But The Bike Shed, Iron and Air, Cafe Racer Dream, Cafe Racer United and Pipeburn are great inspiration as well.

 

If you want just some great cafe racer pictures to be inspire by, check out our pinterest board on cafe racers.

First, looks.

 

How to build a cafe racer
These guidelines are just that—guidelines. Designing a cafe racer is as much about art as science, and each bike is different in its own way. It reflects the environment, the era and the owner of the bike. Yet there are things we can do to ensure that the result will look solid and professional.

I’ve been influenced by motorbike design for several years, and have built my own cafe racer. I based it on the same observations that I’ve sketched out here. Hopefully they’ll inspire some fellow builders to invest time into the aesthetics of their project.

 

How to build a cafe racer
To illustrate the points, I’m using the Bike EXIF calendar cover star: Mateusz Stankiewicz’s Honda CX500, built in conjunction with the garage Eastern Spirit.

 

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THE FOUNDATION The foundation contributes most to the structure, direction and general ‘easiness on the eye’ that makes a bike a café racer. First, the simple stuff. Café racers are defined by the flat line that runs front to back, giving an uncompromising look and lending strength and speed to the design. It’s a good idea, though not vital, that this line remains uninterrupted. (The perfect example of this rule being broken well is the Wrenchmonkees’ Laverda 750.)

This line is the first one your brain will ‘see’ and will guide your eyes along the length of the bike. If there are kinks and breaks then it eliminates continuity and, like bumps in the road, makes the experience uncomfortable. This powerful base sits above two fairly evenly sized wheels.

 

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THE ‘CUT-OFF POINTS’ These lines are the wheel centerlines. Anything going beyond these lines will serve to make the bike seem ‘odd.’ Too much over the rear wheel will make the bike seem rear-heavy and poorly planned. It’s quite common for bikes to do this, however, and it’s not a big deal if crossed over by a small amount—as in our example.

If you do go too far over, then minimize the depth of the seat or cowl. There’s nothing worse than a big cowl hanging over the back end of the bike. The front is less of a problem but front fenders cut on this line look best.

 

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HEIGHT LIMIT Just as important as the cut-off points. The height limit gives a planned look to the design. Defined as the highest point on the fuel tank, anything protruding much above this point will take away from a café racer’s sleek and streamlined looks. It will also serve to make your bike look more like a tracker and less like a café bike. Keep it low and keep it clean. Combined with the cut-off points, this imaginary box should contain all the major elements of your design.

 

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THE ‘BONE LINE’ Hugely important in car design, it is very important here as well. The bone line serves to describe where the widest point of your bodywork is. This is where your reflections on your seat, tank and lamp will fall. Think of the ‘bone’ as the 3D brother to the more 2D foundation line. They work together as a team. Here the center of the lamp is right on the bone line: A great decision that ties the whole upper together.

If you get anything right it should be this. It immediately makes the bike look like it really belongs together and is not just a jumble of parts. Next time you see a bike (or indeed a car) you like, take some time to see if it has this central ‘bone’ and where it sits. This Honda is a perfect example and, though it’s not the first thing you might realize you see, it’s why this is not just a good bike, but a great one.

 

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THE VISUAL WEIGHT This is where the main ‘mass’ of the bike is, and it can be split into two parts. Firstly, the main mass is the engine—including the cylinder/crank/gearbox, or anything towards the front of the subframe. This is your tank parameter. A tank longer than this will look overly big and heavy, and a smaller tank will look like the bike has outgrown it—almost bobber-like.

Secondly, and just as importantly, is the axis of the visual weight, seen here in the middle. This is usually defined by the middle of the engine, or more accurately, the middle of the cylinder/piston. This will define the ideal shape of the tank. The peak of the tank should fall right on or very close to the axis. It is amazing how much more robust and ‘sporting’ a bike looks when this is incorporated into the design.

It applies equally for bikes such as Hondas, Kawasakis and Yamahas that have inclined engine blocks. The axis still falls through the middle of the cylinder at that angle. The result is that these Japanese bikes look better with tanks that peak towards the very front of the bike and taper off towards the rider.

 

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THE SWOOP Ideally you want the seat and the tank to look like they belong together. We can do this by making sure the curve of the tank flows into the curve of the cowl. This will make it look almost like the tank and the seat were once a single piece of metal, and someone scooped out a place for a rider to sit. It makes it look intentional and tight.

 

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PRIMARY ANGLES Often overlooked, the differing angles on a frame with those of the forks, shocks and other parts can make a spaghetti of lines which could ruin all your hard work. Be considerate of them when adding new parts. Here this bike has a brand new subframe to clean up the wobbly CX500 original. The builder has very cleverly matched the angle of the front fork, making it look cohesive. Angles are something we take great care of when designing cars too.

 

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SECONDARY ANGLES Even in small areas, the builders have tried to make parallels of two or more angles on different parts. This is some subliminal stuff right here. You might not notice it—but you can bet that your brain does on a certain level.

 

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FORK DISTANCE Keep the front wheel as ‘tucked in’ as possible. It gives a bike a ‘pouncing’ and aggressive stance. I know a fork swap might seem like a good idea, but don’t make it look like a chopper, OK?

I have seen bikes that match this guide to the letter that look great. And I have seen bikes that disregard them totally, and still look amazing. Following these guidelines will give you a base on which to work and help understand why a bike looks like it does.

Once aware of these ground rules, it’s up to you how you choose to stick to them—or break them.

 


 

And then the performance:

 

Building a cafe racer

The first feature on ‘How to Build a Café Racer’ struck a chord. Not everybody who read it agreed with the content, but when it comes to style, there are several different schools of taste.

I’m going to focus on the performance side of building a cafe racer. Or street tracker, scrambler, or any custom motorcycle, for that matter. Let’s start by picking the right bike up front to avoid expensive mistakes down the track.

 

Building a cafe racer: Yamaha
1. Choose your weapon. The most affordable motorcycles to customize are the bikes that time and style forgot, and many are Japanese. That means the Honda CBs, in the 350, 360, 500, 550 and 750 capacities.

Yamaha has the XS series, in 360, 400 or 650 capacities. Forget the XS500 or TX500, unless you’ve got tons of time and money. Then there’s the SR400 and SR500, and even the Viragos are now getting lots of attention.

From Kawasaki, you can pick a Z of any size. But it was Suzuki that produced some of the best air-cooled inline fours, like the GS750/1000s—which is why Pops Yoshimura gave them so much love. And why you see hardly any for sale these days.

 

Building a cafe racer: Mule Motorcycles XS650
2. Know the issues. All these bikes will most likely have the same issues, because they were all manufactured at least 30 to 40 years ago. We’re talkin’ about the 70s, when bikes were gaining power with each new model year but the handling was lagging behind.

By 1972-73, almost every bike was sporting a disc brake up front. Intake noise was still audible, and most wheels had wire spokes. Shocks were mostly chrome spring holders, and low-hanging mufflers and centerstands caused lots of sparks (and crashes) when cornering at speed.

Lessons were learned and improvements were made. As the bikes were pushed to their performance limits at the racetrack, improvements gradually made their way into production models. These lessons, tricks, new parts and tuning secrets have since continued to gather, so we now have a huge pool of knowledge.

I should mention it’s always a good idea to choose a bike that has decent parts availability—plus a wide selection of aftermarket goodies. Putting a lot of effort into a bike that you can’t even buy a head gasket for is the start of a frustrating journey.

 

Building a cafe racer Triumph
3. After your purchase. Let’s say you bought a 70s bike cheap, with the intent of building something really cool to dazzle your friends. Maybe you’ll ride it every day to work or school too.

After many nights in the garage, the bike runs decent and you’ve done all the things that everyone else does to make your bike look cool. But you’re starting to think, “Wow! This thing is like a slow, wobbly 40-year-old buckboard.”

When you go for a spirited ride in the hills with your friends, maybe the bike isn’t all that exciting or confidence inspiring. Or it’s just plain unsafe. Or maybe there are a couple of guys with bikes from the 80s or even the 90s disappearing over the horizon. You’re thinking, “It’s got to get better than this!”

Unfortunately, bikes have been improving at an exponential rate over the past thirty years. But you’re committed to riding your 70s bike, and want to be able to say you built it yourself. It’s time to improve it, while keeping a realistic view of how much you can improve it before you’ve depleted your resources.

 

Yamaha XS650 cafe racer by Mule
4. Make a plan. You’re gonna need a few things. Starting with a direction and gathering knowledge is a must. What can you afford? What should you do? How do you find out, and whom can you ask?

If you search the web and look at pictures of 70s racing machines and hotted-up street bikes, you’ll find clues. The stance was usually changed, as were the tires. Aluminum rims replaced steel, and generic aftermarket shocks and fork kits were installed. You often saw braided stainless brake lines and a second front disc and caliper. Frames were heavily gusseted, and so were swingarms—or they were upgraded with aluminum items.

In the engine/performance department, you’ll need to dig a little deeper: Pictures will show only the external mods. You’ll notice air cleaners, bigger and better carbs and exhausts, and perhaps some sort of oil cooler. To get an insight into internal mods, you’ll need to read articles from old magazines that have hop-up tips pertaining to your bike. And then look for those parts at swapmeets or on eBay if they are no longer manufactured.

Another way to gather knowledge about the older models is to attend a vintage race or two. There are classes for all displacements and different eras. The rules are generally intended to keep the bikes period correct, but most of the parts needed are readily available.

 

Building a cafe racer: Streetmaster
5. Get to work. All bikes like Honda CBs, the Yamaha XS and SR series and Kawasaki Zs can be improved with a standard group of upgrades, beginning with the chassis. Inspecting the frame for cracks or damage is the first step.

Factor in tapered steering head bearings or, at the least, replace the worn out stockers with new OEM bearings and races.

Most of the older bikes came equipped with a plastic swing arm bushing. This should be replaced with a needle roller bearing kit in solid bronze or new-old-stock ones.

Another area of concern would be the swingarm pivot shaft and reducing the side-to-side play of the swingarm down to the factory minimum spec. Up and down movement should be without restriction, but side-to-side or axial play should be almost nonexistent.

 

Building a cafe racer: upgrade your shocks
6. Spend on suspension. It’s time to cut loose. Namely, new shocks and a fork kit. Getting shocks from Öhlins, Racetech, Works Performance, Hagon or Progressive Suspension can all be an improvement.

That said, it’s absolutely critical that the dampening and spring rates are matched as closely as possible to the weight of you and your bike, taking into consideration what type of riding you’ll be doing. Buying a name brand shock that’s mismatched, already used, or designed for a race bike may not yield any improvement whatsoever.

I know that Racetech and Works will build shocks to exactly fit your needs. Lengthening the rear shocks eye-to-eye can get you more cornering clearance and better turn-in for corners. But lowering the back end of the bike, as seen in many current custom builds, has the opposite effect.

The same goes for forks. Scoring a set of cool USD (upside-down) forks on eBay in no way guarantees good handling. But a fork spring and a dampening kit (or Racetech emulators) can yield great results with your stockers if they aren’t bent or rusted. You can even adapt better forks to fit, possibly from a different model of the same brand.

7. Add lightness. Another way to improve the stock chassis is to lighten the wheels and fit better brakes and tires. There may be a similar model to yours that has a lighter, smaller rear hub, or a smaller and lighter disc.

Look at lacing up an aluminum rim, perhaps wider, that allows you to use a better tire. Firestones or knobblies on your street bike are a loud, clear signal that handling in the corners is of no concern, and the other things I’ve mentioned to get the chassis to a higher level will be for nothing.

 

Building a cafe racer: tires
8. Tires. Every tire manufacturer makes rubber donuts in the 18” range that will give good grip and great transitions from vertical to leaned-over. A lot of the 70s-era bikes—almost all except those in the sub 450cc range—came with 19” front wheels. These combined a steel rim with a large diameter, and generally speaking, a much more ‘relaxed’ steering head angle. This increases the gyroscopic effect and leaves you with a bike reluctant to lean or steer into a corner.

9. Brakes. While we’re up front, how about braided stainless brake lines and new pads? Discs can be swapped out for a larger disc from another brand or model, or you could even swap the front hub for something that originally came with two discs.

Note: make sure you also pick up a brake master cylinder intended to push enough fluid for two calipers! Many older bikes had caliper lugs on both fork legs, but oddly no caliper was attached. When you visit the vintage races, you’ll observe that most bikes will have been converted to aluminum rims with an 18” wheel at the front and most likely a second disc.

Other factors are the steering head angle and triple clamp offset, which feed into the “trail” part of the overall package. That’s a discussion for another time, but it’s a huge factor in handling.

 

Building a cafe racer engine
10. Get your timing right. Ok, so now your bike goes straight when you want it to. It doesn’t wobble and the new wheels and tires—being lighter—feel pretty darn good going into and through corners. Not to mention the dual discs slowing the bike down with much less effort.

But if only it had more power! Well, the solution isn’t as obvious you’d expect. At first, anyway. The guys who have been successful at competition over the years don’t just throw some trick component at the bike and go faster. They keep the stock engines or modified engines in top condition throughout the year.

They aren’t up all night playing World of Warcraft. They’re in the garage setting the timing over and over till it’s perfect. Or resurfacing the head and cylinder, so with a new gasket, it won’t leak—ever.

So start by making sure the engine has good compression on ALL cylinders. Check the points are in good condition, and the engine is timed correctly. The air cleaner(s) need to be clean, and the carbs jetted properly—since you tossed the airbox and installed the cool “pods.”

 

Building a cafe racer: big bore kits
11. Rebuilding the engine. Most bikes from the 70s are tired, pooped out and thrashed. A paintjob won’t get it down the road any quicker. You may need to bite the bullet with an engine rebuild, and once again, the vintage races could be your best source. The Yamaha TT500s (with the same motor as the XT and SR500s) are probably the most popular bike in all flattrack races, week in and week out. With a 540cc kit, a Megacycle cam, a Sudco 36-38mm round slide carb kit and just about any pipe, you’ve entered another world of performance.

Same with an XS650 Yamaha. A 750cc kit, Megacycle cam and some 34mm carbs—and CB750s look out! That is, unless your CB owner got a hot cam, a 836cc big bore kit and some Keihin CRs while building his own cafe racer, and paid attention to his chassis set-up.

 

Building a cafe racer: Keihin CR carbs
12. Learn from the hot rodders. The common thread on all these bikes is giving a crap about the chassis set-up, getting the motor at the least back up to “Blueprinted” stock and then using all the standard hot rodding techniques racers have used since the internal combustion engine was invented.

Bigger displacement, more cam, better ignition systems, bigger/better carbs and you can even install exhaust systems that yield more power and are still quiet. There are so many parts available for the older bikes that have evolved over the last thirty years; everything can just be purchased and installed with vendors providing detailed instructions and technical assistance.

Good luck with the project!

 

Those contents were writen by  | On Cargo Collective and | Mule Motorcycles

 

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