WE RIDE A MECHANICAL ENGINEER’S FC350 DREAM BIKE

Oct 25, 2023

With a background in mountain biking and a degree in engineering, Billy Wight has a mindset fueled by data and operated by high-tech software. Since Billy had an engineering firm before he launched Luxon MX, his “startup” aftermarket company was able to jump into the industry with a solid platform to originate from. By sharing software and machinery between both of his companies, Billy has been able to stay afloat through the highs and lows of the motocross economy, and he’s been able to develop and manufacture quality products.

With his “mechanical engineer” status and passionate blog posts on the Luxon website, Billy had a clear path to follow when building his FC350 “dream bike.” It had to be lightweight. It had to be perfectly tailored to his needs, and it had to have some exotic trickery spread throughout.

WHAT BILLY USED ON HIS BIKE

Triple clamps are the staple product that Luxon MX produces, and although Billy is working on the Gen3 clamp right now, we tested Billy’s 2021 Husqvarna FC350 with Luxon MX Gen2 clamps. We previously wrote about these in the January 2022 issue of Motocross Action, and our test riders loved them. Josh Mosiman raced with these clamps on his GasGas MC150 and MC250 two-stroke at the 2023 World Two-Stroke Championships, the 2022 AMA 450 National at Fox Raceway on our 2023 KTM 450SXF test bike. Another interesting note about these clamps is that when you buy a set of MX-Tech Blackjack forks for your Austrian bike, MXT sends you a set of Luxon Gen2 triple clamps—crazy, right?

MX-Tech has developed its own proprietary 49mm A-kit fork that slides right into the stock Honda and Kawasaki triple clamps, but it is too big for the stock KTM/Husky/GasGas clamp, due to the WP forks being 48mm in diameter. Rather than manufacture a completely different fork for the Austrian bikes, it made more sense for MX-Tech to partner with Luxon and sell a custom triple clamp with their Blackjack forks to mate the 49mm bump stoppers to the Austrian chassis. Because Billy is big on the techno mumbo jumbo, we asked him about the flex difference between 49mm MX-Tech forks and 48mm WP air forks. We figured bigger equals stronger and more rigid. In this case, we were wrong. Billy explained that the MXT forks use thinner-wall tubes, which actually makes them 2 percent more flexible.

Billy ran an MX-Tech National shock with Luxon’s adjustable linkage arm in the 3mm-longer position. The linkage arm was mated to the Luxon MX bell crank, which also has geometry specifically tailored to work with the MX-Tech National shock. The linkage bell crank is lighter than stock, and it works together with the shock to produce a more linear damping curve. The linkage used titanium bolts, and it rotated on Luxon’s ultralight linkage arm races—another technical Billy Wight piece that reduces weight.

Billy also added his Luxon MX lever clamps, oil-filter cover, and his lighter and stronger-than-stock rear brake-caliper carrier. The Luxon MX axle blocks have tighter tolerances, and both the left-side block and axle nut are sealed up (factory style) to keep dirt from collecting inside. The only downside is you can’t use a triangle stand anymore. Also, Billy used his resources to modify the stock engine mounts by cutting out the center. Then, Billy hard-anodized the engine mounts, the swingarm and the radiators to a matte black finish, giving his bike a custom look.

Because he wanted to try two different steering stabilizers, Billy welded both HPSD and parabolic damper mounts onto the steering tube of the frame and powder-coated them black. After testing on the track and in Grand Prix off-road races, he chose the Precision Racing Parabolic steering damper system. Because the steering damper sits above the handlebars, he couldn’t run a standard bar pad. Most would simply cut their foam pad, but Billy likes the look of a crossbar, and he can do whatever he wants. He used Phoenix Handlebars’ non-crossbar-equipped 118 bend (in the 80mm height) and made his own custom Luxon MX crossbar out of carbon fiber. He rubber-mounted it to ensure the bars could still flex. From there, he used Phoenix grips and a Motion Pro Titan throttle tube.

Other parts included the rubber-mounted Husqvarna skid plate and an RK Extreme Performance UW O-ring chain for longevity. He used a stock two-stroke KTM air-filter cage (without the backfire screen) and a No Toil air filter, Guts Racing ultralight seat foam with a ribbed Velcro seat cover, and FasterUSA wheels using D.I.D. ST-X rims and black hubs, Pirelli MX32 tires, and Renthal sprockets. MotoStuff provided the footpegs, rear brake rotor and oversized 280mm front brake rotor, brake pads, sharper rear brake pedal tip, titanium axle adjuster bolts, and a titanium bolt kit for the engine.

Billy’s FC350 had a Dirt Tricks front sprocket dome washer, Dirt Tricks cam-chain tensioner, Cycra plastics, and a vented Cycra front fender with an Acerbis front number plate (because the Cycra plate has wraparound plastic, which covers his clamps), as well as Acerbis’ vented airbox cover, frame guards and fork guards. Billy replaced the Magura clutch actuation system that came stock on the 2021 Husqvarna FC350 with a Brembo system off a KTM. He added ASV unbreakable C6 levers, a Fasst Company rear brake return spring, Split Designs custom graphics, an Akropovic exhaust system, and a Vortex ignition tuned by Twisted Development.

After it was all said and done, the total bill for “Billy Wight’s FC350 dream bike” was $29,000. Of course, Billy didn’t pay full pop for each mod, but he still invested a good chunk of change into this project. Was it all worth it? We mentioned earlier that his goal was to build a lightweight bike that was tailored to his personal needs and had lots of exotic parts. This bike achieved his goals!

The air-fork-equipped 2021 Husqvarna FC350, in its stock form, weighed 220 pounds on the MXA scale with all fluids added except fuel. Billy did add weight when he installed the spring forks, more robust wheels, steering damper and mounts, and the skid plate, so he had his work cut out for him when it came time to lighten the bike up. Amazingly, with his lighter-than-stock catalog of Luxon MX parts, lighter-than-stock MX-Tech National shock, titanium bolts and “lighter-than-Dunlop” Pirelli MX32 tires, Billy was able to get his FC350 to 224.4 pounds, a 2.4-pound total increase over stock.

TESTING BILLY’S DREAM MACHINE

Of course, the MX-Tech suspension was sprung and valved for Billy’s weight and skill level. But, luckily, MX-Tech suspension is known for having a plethora of clicker options for fine-tuning, as well as all the factory-looking friction-reducing coatings. MX-Tech also prides itself on creating lightweight products, and maybe that’s why they get along so well with Billy. Of course, the MXT Blackjack spring forks aren’t as light as the WP XACT air forks, but Billy explained that they are lighter than a Kayaba spring conversion kit. Billy’s suspension was set for a Vet Intermediate who weighed 210 pounds. It wasn’t optimum for our Pro test riders, as it needed lighter springs and stiffer valving, but Billy likes it, and that’s all that matters. The same goes for the steering stabilizer. We didn’t need it on the National track at Glen Helen, and it took some time for our testers to adapt to it, but Billy appreciates it.

As for the FC350 engine, our testers were blown away. With a 14/52 gearing, Akropovic exhaust and Twisted Development-tuned Vortex X10 ECU, the FC350 was everything you’d expect from an “engineer’s dream bike.” Our test riders could stay in third gear all the way around the Glen Helen track, making it feel almost like an automatic transmission! Billy added the titanium Akropovic exhaust because it’s lighter than stock, and we appreciated it for how beautifully quiet it was. Billy didn’t want Twisted Development to make any engine mods, just mapping. After all, he bought an FC350 because he wanted rideable power. So, Twisted mapped the Vortex ECU to make the most of the stock powerband and matched it to the new exhaust. The two maps Billy chose to set on his handlebar switch were both called the “power map,” but the second one had less engine braking. For Billy, the reduction in engine braking brought back memories of his two-stroke days. It also helped the chassis maintain traction in the rough.

Overall, we were blown away by how much power this bike had. It made huge gains with very little work done to it. The power was incredible. It felt like a factory bike because it was so smooth and fast. We haven’t tested a factory 350 four-stroke in years, but we imagine this is what the latest engine would feel like. It truly makes you a better rider, and it drops lap times. It pulls long enough that you don’t feel like you have to shift and still has enough power on the bottom to carry third gear in turns, which isn’t usually the case on the 350.

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