It's easy to get wrapped up in the details while building a custom motorcycle and forget about the overall stance, complete package, etc. Likewise you can nail the stance and then cut corners on the little stuff and end up with a disappointing pile of compromise. Clay Rathburn doesn't have this problem and is known for his stunning, hand-built motorcycles. Their clean lines and lack trendy frills makes his bikes easy to pick out as Atom Bomb Customs. For this particular machine, Clay kicked classic choppers square in the nuts and made himself a semi-modern dirtbike from scratch and a little help from an old OIF Triumph. It looks so well proportioned and finished from every angle that you could almost think it's a factory dirt bike, though you'd be hard pressed to figure out the exact vintage.

Engine, year and make, model, modifications: 1974 Triumph Bonneville 750; front motor mount removed, various other mounts removed and altered, intake ports relocated 1.5” inboard, exhaust converted to flange mount, more or less stock rebuild with oversize valves and 650 exhaust cam. New Amal carbs, Pazon ignition. Exhaust is stainless, fabricated in house with Burns Stainless collector and muffler. Jeremy at LC Fabrications made the carb tops and ignition cover.

Frame: One off mild steel frame and swingarm built by me. The frame reuses about a 1/2” x 2” portion of the original 1974 Bonneville frame. About the same size as the VIN. Totally custom frame geometry to actually work like a dirt bike.

Tire/wheel size and style: Sun rims on Yamaha TT600 hub in front and lightened Triumph conical out back, 2.75”x21” and 4.00”x18” Pirelli MT43 tires. 

Fork: 43mm KYB, revalved and resprung by Racetech. Originally on a 1983 Yamaha TT600. Shocks are custom by Racetech.

Favorite thing about this bike: Who else would be stupid enough to build this? That’s my favorite thing about it. Really, just being able to get something like this from my head to reality was pretty cool.

Other mods, accessories, cool parts, etc: Hand built fuel tank, center mounted oil tank, and side panels by me; Nickel plated frame, swingarm, headlight and kickstand; Carbon coated fork tubes, hand formed air filter housing, super sweet gas tank vent hose.

On the road or off, this thing rides like a beast. It’s got torque that dirt bikes normally don’t, and it’s big, so it can be a handful to ride hard. I was honestly surprised by how well the damn thing works, the suspension is awesome for being a standard twin shock setup.

Since this was a personal project and such an involved build, I got a lot of help from a lot of folks. Mostly from my wife who put up with this thing being a near obsession for a good long while, but a bunch of industry folks stepped up to help as well:

Race Tech Suspension: www.racetech.com

Burns Stainless: www.burnsstainless.com

DC Plastics: www.dcvmx.com

Carbon Raptor: www.carbonraptor.com

Powder365: www.powder365.com

Rebel Gears: www.rebelgears.com

LC Fabrications: http://www.lcfabrications.com/

And don't forget to check out the Atom Bomb Custom site for more of Clay's creations: www.atombombcustom.com

Photos by Tony Hall