This project should make every bike enthusiast's heart skip a beat: In summer 2023, bike manufacturer Leafcycles launched the Klunker Custom Challenge. The plan: to transform a Leafcycles Klunker into an iconic one-off. One of the customised bikes particularly impressed us from an eMTB perspective: a Klunker with an electric drive. We show you how the one-off was created - and how you can recreate it.
How to convert a clunker into an e-bike
California, mid-70s: these were the pioneering days of mountain biking. A few hippies in the Marin County area pushed their rusty old beach cruisers up the mountains and then rocketed back down the dusty Fireroads. The voluminous tyres and, above all, the central tube mounted in the main frame triangle were classic for this type of bike. The bikes were often modified with motocross or BMX handlebars and drum brakes to make the handling a little more controllable for the hellish downhill ride.
Klunker bikes are cult today, because they epitomise the beginnings of MTB sport. They are representative of a time when independence, freedom and individuality characterised the zeitgeist. The Leafcycles brand has taken up this spirit of the times and called for the official Klunker Custom Challenge in July 2023.
Leafcycles is normally better known for dirt bikes made of CroMo steel, but the Augsburg-based company's range also includes an iconic replica of the former Klunker. This replica served as the basis for the challenge. The task: you had to send in a concept on how to turn the Leafcycles Klunker into an iconic one-off. Anyone whose concept was convincing received a complete Klunker bike at a preferential price - with the condition that it be converted according to the concept submitted.
Tyre manufacturer Maxxis also took part in the Klunker Challenge with a design. Their initial idea was to deliberately give the frame a rusty patina to give the bike a certain vintage look. They also decided on a single-speed drive - after all, less technology also means less stress. But when your knees start to tweak here and there, you sometimes secretly wish for a little more gear variety. Or alternatively: a little assistance! And it was precisely at this moment that the idea of converting the Klunker into an e-bike was born. Of course, without spoiling the iconic look of the bike. What's more, the whole thing had to be as inexpensive as possible. Anyone should be able to rebuild such an E-Klunker at low cost and with a little manual dexterity.
Event and team manager Lukas Damm was in charge of the project for Maxxis. We wanted to know from him how the Klunker conversion actually went:
The search for the right drive
For Lukas, it was clear that the motor should be as small as possible. At the same time, the question arose as to how to hide the battery as stylishly as possible. Google was supposed to help answer many questions, but the sobering answer came quickly: a rear wheel hub motor that met the requirements - low cost, 110 millimetre installation width - was not so easy to find. In the end, they came across the Chinese e-motor manufacturer Keyde. They not only have a front hub motor in their programme, but also a battery solution in the form of a stainless steel drinking bottle. The S100 front motor is extremely small and has an output of 250 watts. "What's special about this solution," explains Lukas, "is that the motor is connected directly to the battery. It is controlled via Bluetooth. A pulse generator on the crank sends a signal to the app as soon as you pedal. The app then controls the power output of the motor. This eliminates the need for any control unit on the handlebars." Particularly important in the case of the Klunker conversion: the cockpit remains clean and tidy. The motor also has a 6-hole mounting for brake discs, which makes it possible to fit a disc brake on the front wheel.
The choice of components
The bike and all the e-motor components were the first to arrive. Then came the question of the paintwork and the fitting of components to complete the e-bike bling. "The most important thing for us was to realise the project on as low a budget as possible and at the same time make the Klunker look cool without compromising on functionality," says Lukas. The motto was: "Before ordering anything, always take a look in the box of old items or complaints first. Maybe you can save a part or two from the bin." Many bikers who want to build a bike on a small budget would probably proceed in a similar way - first look in their own junk box, then either on eBay or at the next bike flea market.
It's time to get down to business - the remodelling can begin
What goes better with a real bling bike than the rustic look of bare steel? But the clear coat and phosphate sealant had to come off first. The cheapest stain from the Bauhaus was supposed to do the job - but far from it. Despite being applied according to plan, the paint didn't want to give up so easily. "For some reason," explains Lukas, "the stain, clear lacquer and phosphate coating turned into a tough, sticky mass that just wouldn't come off the frame. After a few days of drying out, heavy artillery was brought in: The Klunker frame was sanded down to the bare steel using an angle grinder with a knotted wire brush. The result was the look that the final bike was to have.
The next step: spoking the wheels. "Even if it's a bit Messi-esque," jokes Lukas, "in my private life I sometimes spoked old wheels and sorted the spokes neatly by length". Even though the chances of reusing them are probably close to zero, in this case the bunkering turned out to be a jackpot: "I actually had all the spoke lengths I needed." There were also old used Kartell platform pedals, a few BMX cranks, a used chainring mount including chainring, a never-used Dirty Steel BMX prototype stem and a used brake disc. Even the brake levers, brake calliper and grips were still lying around in storage. All parts that would never have found their way into the sale.
"Well, as a company in the bike segment, you're at the source in many cases," admits Lukas. "And the tyres naturally came from our own stock. The only two parts we had to buy in separately were the Brooks B17 saddle and the gold chain. Sometimes you just have to turn a blind eye and make additional purchases."
How much does the fun cost?
Finally, the question: How much would it cost to convert such a clunker into an e-bike if you wanted to invest as little as possible? In this particular case, it was a little more complicated with the motor. If you make an enquiry on the Keyde website, you will receive a weekly quote, as the prices there are linked to the US dollar. If goods are not in stock, Keyde takes care of the import, customs clearance and delivery to the customer. The following parts were used for the conversion:
- S100 front motor with Bluetooth: 249 USD
- BI3607 battery: 279 USD
- BBC 1T1 Cable: 12 USD
- Pedal sensor: 39 USD
- BTB140 BT-Button: 29 USD
- Total: 608,- USD plus import, customs and shipping
Just to throw a realistic figure into the room: this engine set is available at home for around EUR 850. At the time of the Klunker Custom Challenge, the Klunker cost between EUR 599 and EUR 739. Normally you can already convert the Klunker into an e-bike with this minimal set, but we would definitely recommend a front disc brake. Estimated costs approx. 30,- EUR. The cost of a customised Klunker with e-drive is therefore around 1500 EUR (minimum version). The rest depends on what other components you install.
Josh Welz
Editor-in-Chief
