Madboxer: homemade Subaru-powered madness

In the world of custom bikes, there are few bigger challenges than to build a bike around a car engine. They’re heavy, torque-focused, and trying to physically fit one into a standard motorcycle frame is easier said than done.

But what if your starting point is a car engine and you build everything around it? That’s what Hawke's Bay local Marcel van Hooijdonk did to create his incredible Madboxer custom.

The Madboxer, as good a name as any, has been in the build for more than five years.

A toolmaker by trade, Marcel is more than a dab hand with a set of tools, so when a friend sent him an email with a photo, issuing a challenge, he leapt at the chance to put his skills towards something a little different.

“It all started off as a bit of a challenge from an Aussie mate, Harry, who came across an artist’s impression of a concept Subaru-powered bike with the comment “something for you to knock up in the shed, mate” says Marcel.

The Subaru engine was the key to this build, and Marcel had a few options to choose from when it came to which to build his bike around.

The most readily available Subaru engine in NZ is the long-lived EJ series, with engines ranging from 1.5 to 2.5 litres, found in most Subarus since 1989. But it wasn’t the ever-popular 2-litre Marcel ended up with, rather a turbocharged EJ25 out of a second generation NZ-new WRX became the heart of the build.

To start the project off, Marcel eyeballed it to see if it was even possible to turn the Madboxer idea into reality.

“I got a motor case, some tyres, spaced it out, stepped back and grabbed a beer,” he says.

After eyeballing it and putting together the mental plan on just how to proceed, the decision was made. “Yes, it’s doable.”

Now committed, Marcel had to lay the groundwork for his build with some serious computer time. Like all serious builders, he started with a computer and putting together a CAD drawing and getting signoff from LVVTA NZ.

“Once I had placed motor block and wheels in place, I started in AutoCad, making drawings of centre steer hub, swing arms and main chassis sides,” he says. The drawings were also used for programming of the CNC milling centre and lathe to carve out the individual pieces of the bike ready for assembly.

It wasn’t a straightforward job, however, and took a few tries to get everything just right, with Marcel needing to work out a system of steering the twin-swingarm design that met with the approval of the certification panel.

Through the long build time, the bike slowly took shape, with a Kawasaki fuel tank, online-sourced wheels, and a smaller twin-turbo Subaru Legacy primary turbo replacing the big WRX turbo.

The result is an engine that runs very smoothly Marcel says, even though it has no real flywheel as such, with Marcel opting for a modified Japanese 2-speed, automatic transmission then using a chain drive to get power to the rear wheel.

Like other “automatic” motorcycles, there is no gear lever on the footpegs, rather a button on the handlebar to change gears while braking is just like a scooter with a bar mounted lever for the Buell-sourced brakes.

With all that work gone in, it would be a right shame if it was all for a trailer queen, and thankfully Marcel fought it out with the LVVTA Certification Panel and won the day.

“Being able to ride it was the aim right from the get-go,” Marcel explains, “and as a result it did impact on the final design. The system here in NZ is not too bad. You forward your design at the beginning and a panel go over it.

“Once you have approval you can start, but with inspections along the way you can make changes, you always think of something you would like to change, which has to then go back to the panel. At times it was hair-pulling, but now it’s all done and 100 per cent road legal, I must say it wasn’t too bad,” Marcel says.

The result is a thing of strange beauty. Weighing 313.5kg, it’s heavy by motorbike standards but, being a boxer engine, the bike holds the majority of it low in the chassis. With torque levels most bikes of a similar weight can only dream of, this is sure to fly down the road.

-BRM.co.nz