Bill Brosius has spent his life surrounded by motorcycles, a tradition passed down from his dad, Jay. Father and son would attend motorcycle races together when Bill was growing up, gaining an appreciation for the talent of racers and their equipment.
“I grew up on the back of his bike, from poker run to poker run and every destination a Harley rider would put on their bucket list,” Bill Brosius related. “We would also go to all the roadracing and flat-track races in California.”
The pair closely followed the flat-track racing circuit, spending summers attending races until Bill had to return to school. As a teenager, Bill was taught how to groove tires and change sprockets by a Modesto Harley-Davidson team mechanic, and he was given the opportunity to push out the team’s Harley 883 racebike to the front row of the Sacramento Mile grid alongside dirt-track legends Jay Springsteen, Chris Carr, and Scott Parker.
In 1995, Bill joined his father on a cross-country trip riding on the back of his Electra Glide.
Soon after getting his motorcycle license in 1998, Bill and his father rode alongside each other on another trip across the country.
“He gave me my first cigar at the Sacramento Mile on my 18th birthday,” Bill recalled. “This was the life I had with him and our mutual love for motorcycles.”
With the motorcycle seed firmly planted, Bill indulged in almost everything with two wheels. Along with Harleys, he also rode dirtbikes and trials bikes off-road and sportbikes on the street and the track. But the rides that were most special were alongside his dad.
In 2018, Jay began to notice his balance starting to deteriorate, possibly due to his exposure to toxic Agent Orange chemicals during his military service in Vietnam as an electrician in the U.S. Army.
With Jay’s ability to ride motorcycles in jeopardy and his memory failing, the father-and-son duo set off in 2018 for one last cross-country ride together, with Dad on his Harley-Davidson CVO Softail and Bill on a Sportster 1200. They traveled from California to Indiana where the Sportster would be stashed for use at their family home, with another Sportster back in California.
“I didn’t know it at the time, but that would be our last ride together,” Bill told us. “Over the next year, his mobility decreased to the point that even the small bikes could not be ridden. A doctor later diagnosed him with dementia and found that it was incurable. My father’s health was quickly declining, and the last three years hit pretty fast.”
To provide inspiration for his father, Bill decided to turn his 883 Sportster Hugger into a flat-tracker like the ones they used to watch together at the races. Around the same time, he was able to obtain a mill and a lathe for the bargain price of just $1,500.
“The stars aligned,” he said. “It was like the big man upstairs had a plan!”
With a garage full of bikes and spare parts, Bill began pulling together components for the flat-tracker build. He used his lathe to machine steering-stem inserts to adapt a Showa inverted fork for the Sportster, and he milled spacers to center Kawasaki ZX-7R rotors for use with Brembo 4-piston calipers. Then he milled the Harley’s wheel hub to a size that matched the Ducati-sourced axle.
For the rear end, he used a 19-inch wheel adaptor kit from TC Bros. that helped convert it to a tracker-style setup. The factory rear brake was swapped out in favor of another 4-piston Brembo caliper, and he milled his own mount to get the caliper centered on a floating rotor sourced from TC Bros. He then milled a bracket for a master cylinder sourced from a ZX-7. A pair of 14.75-inch Öhlins piggyback shocks were added to the rear.
The build took a sudden detour when a buddy offered an Öhlins fork with radial-mount Brembo calipers to use on the tracker, so Bill went back to work on the front end. The H-D master cylinder didn’t work with the Brembos, so he used one from an Aprilia RS250. Pro Taper flat-track bars were fitted with a Motion Pro throttle kit.
Next up was sorting the web of wiring strewn around the Sportster.
“My father was an electrician his entire life, and I didn’t fall far from the tree,” he explained. “I pulled all the wires from the handlebars to relocate the ignition, along with the buttons and the ignitor coil. Without my father’s teachings throughout the years, I would have never been able to complete that or even have attempted it.”
What began as a budget build took a new turn when Bill received a sizeable bonus from his employer. He quickly converted his cash into an S&S big-bore kit and cams, a Saddlemen tracker seat, and a Storz XR750 fuel tank.
“I ended up going with Supertrapp exhaust because that was the pipe Modesto H-D used on their Sportster flat-tracker back in the day. My father and I would help that team at the local races as much as we could, so this brought back those memories.”
As the build continued, Bill would send pictures and do video calls with his dad in Arizona so he could observe the process.
“His excitement every time I called was amazing. He knew where I left off and what parts were on order coming in. He loved every bit of it!”
When it came time to decide on paint for the tracker, he followed his father’s off-beat color preferences and selected a stunning blue tone instead of the obvious choice of Harley orange.
As he was polishing up the details on his street-tracker, he would take it out to trackdays to shake it down in a controlled environment.
“Everything has been tested, as fast as I can make this bike go, and it’s a complete blast to ride!”
After a solid year of work, Bill had completed his build and invited his dad to come and see it.
“He was over the top when I started it up so he could hear the machine running! He told me that he was proud of me, and that will sit me for the rest of my life.”
The Evil Twin
The Brosius story is seemingly complete, but it has a second act.
With Jay’s health continuing to decline, Bill was assigned the duty of selling off his dad’s bikes and cars. Flush with cash after another bonus from his work as a maintenance manager – and with another Sportster sitting in his garage – Bill began work on a second street-tracker.
“I wanted this to be the evil brother to the blue bike,” he elaborated. “With my dad’s health, I put everything into the next build to make sure that I got it done in time. I took everything that I learned from the first build and was able to refine and speed up the process to complete it.”
Bill went to work on the Sportster 1200, repeating some of the items and steps from the first build but choosing a different suspension and color palette. A stealthy gray replaced blazing blue, with a greater emphasis on black finishes rather than chrome or gold.
He bought a black Öhlins superbike fork from Kyle Racing, which dialed them in for street-tracker duties. Öhlins shocks were fitted to the rear, only this time in a black finish and 1 inch shorter in length.
“With the suspension sitting lower in the rear, I was able to get more stability on tip-in and roll-out on high-speed corners, which makes it less twitchy,” he reported. “But the additional ride height on the rear of the blue bike makes it a demon on tighter tracks.”
At this point, Jay’s dementia was getting worse, and he struggled to even carry on phone conversations. To keep his dad looped in, Bill began posting videos on YouTube for his dad to watch.
“My mother told me that his eyes lit up seeing the build happening! She would stream it to the TV, and he could feel like he was right there with me as I was building this thing.”
Bill was able to complete the bike within the last couple months of his dad’s life, and Jay was able to be alongside his son as they watched the video of Bill taking the bike for hot laps around Thunderhill Raceway.
“He couldn’t say very much, but I got to see the enjoyment in his eyes while watching.”
Jay Brosius passed away March 26, 2022, at the age of 74.
“To feel his legacy in every ride is what makes these bikes special,” Bill summed up. “I feel my father in every ride.”