Ducati 900SS custom by Atom Bomb

Ducati 900SS custom by Atom Bomb.

With the new-wave custom scene continually evolving and diversifying, it’s becoming progressively more difficult to classify custom motorcycles. Even the mere mention of the term “café racer” is enough to send purists into a frenzy these days. It gets even more complicated when the donors are ’90s-model Ducatis—an emerging trend that we’re loving.

Who better to blur the lines than Clay Rathburn of Atom Bomb Custom Motorcycles? Clay’s a master craftsman whose work we’ve featured multiple times, and who seems to be able to turn his hand to any style of bike. His latest creation is this breathtaking Ducati 900SS-based café-racer-cum-streetfighter.

Ducati 900SS custom by Atom Bomb.
“I traded into a mostly stock 1996 900SS a couple summers ago,” says Clay. “The stock carbs were shot and it had a wiring issue. I put a set of Keihin FCR carbs on it, fixed the wiring, and rode it enough to totally fall in love with the way it made power.”

Unfortunately, Clay soon realized that the 900SS needed more work: “the stock suspension was shot, and I could feel the frame flexing.” On top of that he wasn’t too keen on its looks, so onto the bench it went.

“I guess this project was about building the right home for a fantastic engine, and (as usual) doing something I’ve never done before by building a proper sport bike.” Despite establishing his reputation with more classically-styled bikes, Clay does have some connections to motorcycle racing—Atom Bomb were responsible for the fuel tanks on Danny Eslick’s Daytona 200-winning Triumph 675. “I’ve always loved sport bikes, just never built one from the ground up.”

Ducati 900SS custom by Atom Bomb.
Clay’s original plan was to source a 999 frame to house the 900′s 2v mill—but, since he had a blueprint of the 999 frame, he decided to build one from scratch instead. Using “a calculated mix of tubing sizes and wall thicknesses,” he was also able to brace it better than a stock 999 frame. The suspension geometry is identical though, with the exception of a 23.5 degree neck angle—achieved by re-using the donor bike’s neck.

Since the 900SS was a personal project, the budget was limited—forcing Clay to mix and match suspension components. Up front are a set of Showa forks from a late-model Suzuki GSX-R, set in the 900SS triple trees “because they fit the GSX-R forks, and more importantly because the offset provided the correct trail numbers for the 23.5 degree neck.”

The GSX-R also supplied the Brembo monobloc radial brake calipers, matched to floating Brembo rotors. An Aprilia RSV front wheel was mounted up front, with a Ducati 999 rear wheel, swingarm and shock out back. Clay also fitted an Öhlins steering damper via Atom Bomb mounts.

Ducati 900SS custom by Atom Bomb.
Without any particular direction in mind, Clay set about fabricating all bodywork from aluminum—starting with the tail. “It’s fair to say the shape of the tail was 100% dictated by the 1098 tail light I bought for $20 on eBay. When I got it, it had a LOT more angles than I thought, but I paid for it so I built the entire tail around it.”

He then “played around” with shapes for the tank until he found something that fitted visually. Despite its small appearance, it carries 4.5 gallons of fuel. Other bespoke bits include the foot controls and the front fender brace, which holds a powder coated Ducati performance fender.

The engine wasn’t left untouched—with almost 30 hours spent on the heads alone before being put back together “with a lot of go fast fun parts”. The checklist reads like any sport-bike fan’s dream: in addition to the upgraded carbs there are Fast by Ferracci high compression pistons, ported and flowed heads and manifolds, CA Cycleworks heavy duty head studs and an Ignitech programmable ignition with CA Cycleworks coils.

Ducati 900SS custom by Atom Bomb.
Atom Bomb also lightened the flywheel and installed an aluminum clutch hub, basket and plates, along with a Yoyodyne clutch master cylinder and a heavily modified 1098 oil cooler. The modded engine now breathes out via a hand-made stainless steel exhaust system. “We haven’t dyno’d it yet but based on riding a lot of stock 900cc Ducatis, we’re making substantially more power everywhere in the rev range.”

After a few miles on the road to tune the carbs, Atom Bomb took the 900SS, now dubbed “Eleven”, straight to the track—where friend and experienced club racer Andrew Swenson put it through its paces. “The plan was to take it easy for the first session, adjust what we need to adjust, and ease into going fast. Andrew came around on the third lap of the first session wide open and dragging an elbow, and ended up riding four or five sessions where we had planned to do three.” Since the track test, Clay’s put about 300 street miles on the bike, and claims he’s “never ever had so much fun a motorcycle.”

Ducati 900SS custom by Atom Bomb.
Does this mean we can look forward to more jaw-dropping Ducatis from the Virginian workshop? “I learned a ton about the entire Ducati model lineup while I was building this thing, and of course had a bunch of ideas for the next one while we were putting the finishing touches on. So I’m beyond positive there will be more very trick air cooled Ducatis in Atom Bomb‘s future!”

Clay made a point of thanking the following people for their contributions: Andrew Swenson at Andrew Swenson Designs did the lettering, stripes and painted the timing belt covers and headlight. Shaun Stewart at Slingshot Cycles custom built all of the brake and clutch hoses. TPO Parts sent us some floating rotor buttons to make our front brakes work so much better, and CA Cycleworks helped us out with heavy duty head studs and ignition coils. Big thanks to everyone!!

Images by Anthony Hall.