On The Mark: Harley Sportster 1200S Scrambler

Sportster Scrambler Street Tracker

MX-inspired Sportster scrambler from Purpose Built Moto… 

Last week, we featured the Sportster 1200 Adventure Scrambler from Australia’s Purpose Built Moto, built for workshop owner Tom Gilroy to ride across Tasmania for the film Wide of the Mark.

This V-twin “Tasmanian Tractor” looked amazing, and the specs were quite impressive for a machine that started life as a 589-lb highway cruiser:

  • Wet weight: 225 kg / 496 lbs
  • Ground clearance: 210 mm
  • Front Travel: 180 mm
  • Power: 65 whp

In comparison, the ’06 BMW R1200GS weighed 496 lbs wet, with 190mm front wheel travel and 185mm ground clearance. 

Sportster Scrambler Street Tracker

More importantly, Tom’s hand-built Harley adventure scrambler performed well on the journey, handling a wide variety of Tasmanian terrain:

“The Adventure Harley Sportster scrambler proved itself time and time again on the Wide of the Mark film trip. Handling just about any terrain. The only time I really struggled was in really soft sand, but that could be put down to my skills as a rider too.” -Tom

Sportster Scrambler Street Tracker

After the trip, Tom returned home to begin work on a second Sportster scrambler, this time for a client, Ben. While the Wide of the Mark scrambler was built from a rubber-mount ’06 Sportster 1200C, the donor for this build would be a hard-mount ’98 Sportster 1200S with twin-spark heads:

“While these bikes share the same core DNA, they are vastly different in terms of style, and performance… I wanted to push further in terms of the design on this one, creating a highly distinctive Motocross feel across the whole build.” -Tom

Sportster Scrambler Street Tracker

The entire front end comes courtesy of a KTM 1190 Adventure, while the rear is running a Trac Dynamics billet swingarm and Öhlins shocks — both ends tuned by local off-road suspension guru Charlie Costanzo of Costanzo Racing. Tom says starting with top-shelf components and getting them properly adjusted to work with this specific bike makes the Sportster a dream to ride.

Sportster Scrambler Street Tracker

The bike rolls on a 19″ / 17″ wheelset with HAAN hubs and Excel rims, also sourced from the big KTM adventure bike, complete with the double-disc Brembo front brakes.

Sportster Scrambler Street Tracker

Once again, Tom went with a jetless Lectron carburetor, mating it to a new iteration of the custom airbox he developed for the first build:

“Version 2 sees the set up using a Ducati 1299 aftermarket air filter from DNA filters, a handmade filter mount, and a 3D-printed carbon filament intake plenum that links the two. A bit more work went into this one, but once the Idea worked on our first ADV Sportster scrambler build, it was time to improve the performance of it.”

Sportster Scrambler Street Tracker

On the exhaust side, the entire system and silencer were fabricated in-house from 1 5/8” stainless steel tubing, snaking around the pillion pegs requested for the owner’s son:

“The idea was to create a Dakar-style exhaust that swung low, but was left exiting long and high…working around the pillion peg mounts that were a customer spec’d item so he can take his son for a hoon now and then. The 2-1 system and custom muffler sounds perfect on the thumping V-twin.”

Sportster Scrambler Street Tracker


The engine was stripped and rebuilt with reliable performance as the main goal. With mild cams and port work, along with the Lectron carb and custom 2-1 exhaust, the Sportster put down a solid 75 whp with a properly fat torque curve.

Sportster Scrambler Street Tracker

The tank is from a 2018 Street Bob, while the fenders, fairings, front number plate, and fork shrouds were mainly hand-shaped from aluminum. Then there’s the custom tail section and saddle — Tom’s favorite part of the bike:

“Sharp and thin, the tail protrudes out from under the seat, giving the bike a modern dirt bike edge. Some built-in lighting and hidden mounting keep the finish ultra clean. The seat is set atop an isolated mounting frame, rubber mounted to limit the vibration the rider gets through the seat.”

Tom ditched the original battery box and cover for a late-model unit, mounting it to the frame via a hinge section that unlocks with ¼-turn quick releases.

“The cover allows access to the ignition module, electrics and has room enough for that tool kit you’ll inevitably need at some point of your riding life.”

Sportster Scrambler Street Tracker

The off-road pegs were mid-mounted on stainless brackets built off the case bolts, and the extra offset on the clutch side left room for one of the trickest bits of the build — a small leather pouch with onboard air compressor.

“Actually really handy when you ride off the beach, and back onto the bitumen [asphalt].”

A set of 5″ risers, rubber-mounted to reduce rider fatigue, hold a pair of Pro-Taper Outlaw bars outfitted with ISR levers and PBM switch blocks and scrambler mirrors.

Scrambler Sportster


For the paint and finish, Tom had sketched out a twin bolt design on the tank he liked, but he wanted to give the whole bike that same flavor.

“I enlisted the help of Josh from Ride Design Co. He came and hand-templated the Sportster’s panels and worked up an epic custom graphics kit…black, grey, and red finishing off that track side flavour.”

Sportster Scrambler Street Tracker

All in all, this Sportster scrambler / street tracker weighs in at 203 kg (448 lbs) dry — 42 lbs lighter than stock — with 75 whp on tap. Tom says he’s learned a ton from these two builds, and he can’t wait to build the next one:

“If you want one of these monsters in your garage, get in touch, I’ve got plenty of new ideas to use on the next Off Road Sportster.”

Sportster Scrambler Street Tracker

Build Video

More Photos

Sportster Scrambler Street TrackerSportster Scrambler Street Tracker

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Web: www.purposebuiltmoto.com
Instagram: @purpose_built_moto
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One Comment

  1. Frank Spero

    please tell me are those tires universal sdtreet and off road like were on the Honda scamblers

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