Words: Gary Inman
Photos: Yve Assad
STANDFIRST// Ever wondered why a dirt track bike looks like it does? We asked the builder of this one to explain
Sideburn first saw Weirbach Racing’s C&J Kawasaki in the flesh at the 2014 Springfield Mile. It stood out, to a flat track nerd like me, among over 60 other twin-cylinder framers, because of slightly different solutions to the questions all teams are asked when they start to build a brand new bike. I stared at details like the shape of the fuel tank and the way it sits within narrow twin top rails; the gently curving front downtubes that let the radiator sit clear of the front wheel’s travel.
But, back home in England, poring over Yve Assad’s photos, the biggest question I was left with was, why does a flat track bike have to look like it does?
I love the look of flat track framers, from any era, with any engine. These minimal, muscular machines are the main attraction of the sport for me, but why have the rules been set in such a way that all the bikes use remarkably similar technology? AMA flat track, aka the Grand National Championship (GNC), is no different to any of the major world or national race series – World Superbike, MX1, MotoGP, World Endurance… The rules are set, then tweaked over the seasons, and the factory engineers and race teams very quickly create bikes that push the very limits of legality. Yet I still wondered why flat track’s rules are set like they are. A displacement limit makes sense, but the GNC also restrict engines to a maximum of two cylinders. 19-inch wheels are mandatory (though wheel diameter rules are not unusual in other races series). Streamlining of any sort is banned.
Richard ‘Dick’ Weirbach and his son Ted have strong roots in the sport and in 2011 won what is now the GNC2 class, the Pro Singles support class. Dick has recently been drafted onto the AMA Pro Flat Track’s competition advisory committee, alongside stars like Kenny Coolbeth and Joe Kopp. The committee’s role is to ensure the GNC moves in the right direction. We asked the Weirbachs, are the rules put in place to ensure dirt track bikes remain looking like dirt track bikes?
‘I think there is some truth to that’ says Ted. ‘Also most traditional fans don’t want to see them drastically change either. When the AMA moved away from framers for the singles series, in an attempt to bring more riders and manufacturers to the track, most old school fans didn’t like it.’
For the 2009 season, the AMA banned everything except 450cc motocross-based bikes from their singles championships, in a hope to attract more factory support. It didn’t materialise and many fans disliked the look of the bikes and claimed that in addition the racing wasn’t as good. Entry numbers actually diminished in the top class, but that could have been due to many other factors and a general economic downturn. In comparison, the twins class, where only bikes with custom-built frames (‘framers’) compete, is looking healthy.
‘I think if you look closely at the twins,’ says Ted, ‘internally they have changed a lot, and most of the materials and components that we are using on the bikes have evolved quite a bit. The number of brands has expanded as well and they are becoming more competitive.’
In 2015, the AMA Pro Flat Track main events, the 18-rider finals of the day’s racing and the very pinnacle of the sport, had representatives from Harley-Davidson, Kawasaki, Suzuki, Triumph, Ducati and KTM. For 2015 Yamaha engines will be used too. Look back to the mid-2000s and it was almost a one-make series for the Harley XR750.
‘Everyone has been looking for the alternative to the Harley XR750 for 30 years,’ says Ted. ‘They still win races and championships and work really well for what we do. You can build a high-horsepower bike all day, but if it doesn’t handle, carry corner speed, and then pull like a tractor off the corner without burning the tire up, you are not going to be competitive.’
For years, the adherence to the statement, We’ve always done it this way, seemed to be the very thing that would slowly suffocate flat track at all levels.
‘The sport originated when guys came home from the war, stripped down their street bikes and raced them around horse tracks,’ Ted explains. ‘The simplicity and sound is also kind of the allure.’
In the 1960s, a dirt track race bike looked very similar to the popular high-performance road bikes of the era, a bike a race fan might ride or lust after. Then came Japanese four-cylinder superbikes like the Kawasaki Z1000, Suzuki GS1000 and Honda CB750 and with them a new, production bike road race series. In that era, a race fan’s high-performance street bike looked like a Daytona 200 or Laguna Seca-bound AMA Superbike.
When flat track dipped a toe into the multi-cylinder bike pool, with CB750s and, more famously, the Yamaha TZ700 four-cylinder two-stroke, the AMA quickly agreed with leading teams to ban them. Not because they were dangerous, not because Harley-Davidson said so, but because the decision-makers envisaged a space race that would put flat track team budgets out of the reach of the privateers that were crucial to the sport.
Ted says it’s the same now. ‘In general, the GNC rules are made to keep cost down and competition on an even playing field, thus not letting the guy with the most money win.’
The generation of CBRs, FZRs and 916s meant hot road bikes looked like World Superbikes or MotoGP machinery. As the years ticked by, a dirt track bike looked less like anything you could buy out of a showroom, in anywhere but Japan anyway. But now, with the resurgence of street scramblers and budget custom bikes, dirt track is a major influence again. Not only that, the sport’s blue collar roots are totally in step with a cash-strapped western economy. Conversely, Superbike racing seems increasingly futile (however close the racing might be). It is no longer about making better street bikes, factories are making street bikes that are better race bikes, then backward engineering them for the road.
Ted Weirbach is witnessing the comeback too, ‘There is a great resurgence in flat track right now with GNC1/GNC2; the inaugural X Games flat track race in Austin; the Superprestigio; Sideburn magazine etc [yes, he really said that]. It is hard to find a motorcycle magazine that doesn’t mention flat track. Even many custom bike builders are using flat track influence in their latest projects. That was not the case over the last 20 years.’
He continues, ‘Look at Rossi, Marquez, Bayliss, Hayden, it goes on and on, even down to the new crop of American road racers: Beach, Rispoli, Jacobsen [and the Lowes brothers from the UK]… they are all flat trackers. Sliding a bike on dirt has become a main focus of their training. Even the motocross crowd is building flat track bikes. The future of the sport is bright.’
Which leads us back to this bike. Weirbach Racing own an XR750 and ran a Suzuki SV framer with some level of success, but when building a new Expert Twin, they chose the current go-to engine, Kawasaki’s 650 ER-6 Ninja.
‘A couple years ago it was the option that made the most sense for many reasons,’ Ted explains. ‘The Kawasaki motor is dependable, affordable, has had lots of development and some proven success. We wanted to be competitive right away and the Kawasaki was the best option.’
For 2015, the team has a new rider on their bike, Mikey Martin replacing Rob Pearson. ‘We rejoined forces with Mikey Martin, who we won the GNC2 championship with on our 450 DTX Hondas in 2011. After he parted ways with the folks at Triumph, we decided to put the team back together. So the only real change from these photos is the number plate. We have three Kawasaki twins at present: two with 750 engines and one 700cc that is purpose-built for half-miles.’
While road race teams have been using aluminium chassis for decades, flat track exclusively uses steel for its twins, despite most of the motocross-derived Expert singles and GNC2 bikes having alloy frames and swingarms.
‘Every track is different in GNC racing and this is still the best all around solution for handling and getting power to the ground,’ says Ted. ‘Steel frames provide the right amount of flex without cracking. C&J racing frames, made by Jeff Cole, are our frame of choice for all three of our Kawasaki twins, and they are the preferred frame of many GNC riders and owners.’
Another anachronism with flat track bikes is the front forks. Even the champion’s no-expense-spared machinery relies on RWU forks from a 15-year-old Japanese supersport 600 (but with internal changes). Ted explains, ‘They are tough and work well for what we do. Most of the later model suspension is either too tall or too short for us to get the preferred ride height and give us the correct amount of suspension travel.’
A flat track bike looks like a motorcycle a six-year-old would draw. Big engine, big wheels. The petrol tank is that size because it only ever needs to last for 25 miles at most. The short wheelbase and steep geometry has been reached after decades of tweaking. It’s on the knife edge of stability on the straights, but nimble in the turns.
Handlebar styles have changed greatly since the 1950s, but they’re still cowhorns, terrible for aerodynamics, ideal for mid-corner control. They force riders into the traditional fork-leg-grab crouch on the short straights, another unique element of the sport. Meanwhile, those fat, high-profile Dunlops are ‘spec’ tires, everyone in the GNC must use them. The tread offers a compromise between grip and slip on the wide variety of dirt tracks the series visits, though probably is rarely the very best for any of them, compared to if the riders had an unlimited choice (and testing time) of any tire available.
Whatever the reasons are for the rules being the way they are, flat track is not going to radically change until fossil fuels run out, environmental pressure bans racing or some other seismic change occurs. This is the way it’s always been done and this is the way it’s staying. We’re fine with that.