Master Stroke Purpose Built Moto S Svelte Yamaha Xs650 Chopper

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They say that perfect is the enemy of good. But when it comes to high-end custom motorcycles, shouldn’t perfection be the goal? Having never built a custom motorcycle in this style before, that’s the standard that Purpose Built Moto set for themselves with this Yamaha XS650 chopper.
Delays with parts and other builds meant this project took the Australian workshop more than 18 months to complete. The silver lining was that this extensive time frame meant they could pore over every detail in the pursuit of perfection.

“There are plenty of Yamaha XS650 chopper builds out there,” says the workshop’s founder, Tom Gilroy, “but there are very few that look well laid out and finished right. Generally, kit frames make the bike look too long and punch the steering angle out too much. We wanted a fast-handling, performance chopper.”
Purpose Built Moto started by stripping the bike down, lopping the rear half of the frame off, and setting the headstock in a jig with a rake of 27 degrees. Then the real work began.

Using chromoly tubing and early XS650 axle sliders, the team fabricated a new hardtail section for the back. They kept it narrow and compact, narrowing the rear wheel hub width and shortening the wheelbase by two inches. The bottom engine rails were sleeved in the process, and the frame was braced to keep unwanted flex at bay.
Tom had sourced a classic Banana tank for the project, but it wasn’t going to work with the factory backbone without some modification. Instead of re-tunneling the tank, PBM adjusted the frame backbone by lowering it. While they were at it, they braced the downtube for even more strength.

“Once all that was done, it may have been easier to just rebuild the frame from scratch,” laments Tom. “Build and learn, I guess.”
With the tank sitting pretty and the frame mods done, attention turned to the wheels and front end. Mullins Chain Drive in the USA supplied the super narrow yokes, while lowered 39 mm Sportster forks were slid into place.

The wheels are from one of PBM’s favorite suppliers, Jonich, and measure 21” at the front and 19” at the back. They’re completely bespoke, right down to the custom-width hubs with Jonich’s proprietary nipple-less spoke system. The Mullins Chain Drive yokes are designed for skinny brake-less front wheels, but Jonich was able to help PBM squeeze in a custom front brake setup.
The crew used a custom rotor for the front, cut to size, and adapted a two-piston Brembo caliper from a KTM enduro bike to fit on a custom mount. The rear brake setup is custom too, using the caliper from a Ducati Monster.

The cockpit is equally interesting; the low-rise handlebars and narrow bar clamps come from a downhill mountain bike. The clamps were welded directly to the top yoke and then blended in for a flawless finish, and the bars were fitted with a new throttle, a Kustom Tech lever, and leather-wrapped grips.
The 3-button switches and 4.5” LED headlight are from PBM’s own parts catalog. The headlight sits in a handmade nacelle, mounted to the forks via custom clamps. A tiny speedo sits off to the left of the bike, just below the fuel tank.

Given how much work had gone into the bike already, the guys felt that the engine also deserved a glow-up. In went a Hoos Racing 700 cc big-bore kit, a Shell #1 camshaft, and a new lifter. The head was ported, polished, and treated to new valves with Kibblewhite springs.
An XSCharge E-Advancer ignition and a performance coil produce a mighty spark, with a giant pair of Mikuni TM flatslide carbs feeding the engine. PBM installed a new Barnett clutch, converted it to hydraulic, and hooked it up to a foot control.

It’s the supporting parts that truly shine on this build. The traditional bobber is suspended on a custom linkage that’s as much about art as it is design. An intricate sissy bar adorns the tail, with a jockey shifter lower down that matches its design.
A classic blue and silver paint scheme ties everything together flawlessly. The subtle detailing on the tank and the timeless proportions of the bodywork are divine, as are the countless details littered all over this machine.

“Now complete and run in, Purpose Built Moto’s first chopper build is something I’m proud to stand behind as a great example of where our skills have brought us,” Tom says, positively beaming. “There were some firsts for us on this build—including the extensive work on the motor, scratch-built hardtail, modified frame, and that weird spring-looking thing under the seat.”
Full of fluids and ready to ride, PBM’s first Yamaha XS650 chopper weighs in at just 158 kilos [348 lbs]. With that low weight, a hot (and reliable) motor, and looks to match, Purpose Built Moto may just have achieved perfection.
Purpose Built Moto | Facebook | Instagram | Images by Brandan Trudinger




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