Ducati 900GTS to XR900

One man’s transformation of a Ducati 900GTS parts bike into a sweet flat tracker dubbed the Ducati XR900.

| May/June 2012

Ducati XR900
Claimed Power:
57hp @ 7,700rpm (stock)
Top speed: 121mph (period test)
Engine: 864cc air-cooled OHC 90-degree L-twin with 900SS pistons and twin-spark cylinder heads, 86mm x 74.4mm bore and stroke, 9:1 compression ratio
Weight (w/half tank fuel): 436lb (198kg)

It took more than a second look to register the fact that the bright orange bike standing out from a gaggle of modern Italian motorcycles was actually a Ducati and not a Harley. But it only took a split second to appreciate that this bike was something very special.

Intrigued, I hung around and was lucky enough to meet Peter Koren, the bike’s owner. And when he started to describe how he built the bike himself, from scratch, I was left more than a little impressed. While the Harley-Davidson XR dirt tracker is a cult machine in its own right, favored by the likes of the late, great Evel Knievel and racer Cal Rayborn, Peter’s audacious and unexpected Ducati-based take on the XR works beautifully. You’d think it was a factory machine — but from Bologna or Milwaukee?

Transforming the Ducati 900GTS

“It was an abandoned project based on a 1979 900GTS I’d bought for spares for my 750GT and 900SS,” Peter explains. “But though covered in rust and missing parts, it was, on closer inspection, too good to break. I thought of building a Z-stripe Sport utilizing some parts I already had, but then it sat in the shed for two years while the idea of a flat tracker-style bike came into my head.”

Peter’s styling cue for the flat tracker might have come from the prettiest of them all, but he knew straight from the beginning that there was no point buying up loads of XR parts to make his bike. “A correct XR tank would never fit the frame,” Peter says. “I needed brakes, so I couldn’t run with a spool hub. I also had a fixed, low budget, as it was a bitsa. So as a starting point I bought a replica XR seat base and bars and began from there. I wanted it to look as if it had come out of the Ducati factory.”

Peter’s a little reticent about his many skills, but to build what was in his head, he just got on with it, he says. “I knew I’d have to make the tank myself, to enlarge the whole thing by 10 percent, so I made a wooden buck, got a sheet of aluminum, stole a croquet mallet from my kid and started bashing. I also realized I had to learn to gas weld aluminum to join up the bits — a two-piece base, two sides, one top and the tunnel — that was tricky!” Like the tank, Peter also made the side panels from 2mm sheet aluminum, in a similar manner. “The XR doesn’t have side panels as such, so I looked at the shape of the seat unit and the completed tank, and also took Ducati inspiration from my SS and GT side panels. I also added air scoops to break up what would have been large slabs of bodywork. I fabricated a steel seat pan, which was upholstered beautifully by a local fellow, Earl.”

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