Remember Yamaha RXZ Twinboss twin cylinder two-stroke? We do too, because it never existed – except in the mind of Irvan Cheng.
A Malaysian custom builder who goes by the name FNG Works has masterfully combined two Yamaha RXZ 135 engines to such a degree that you could mistake it for a factory unit. But what impresses us most about this hand-built dragster It's not its bespoke powerplant, its custom chassis or its eerily perfect proportions. What makes it special is the epic journey Irwan took to bring it to life.
The seed was planted six years ago when another custom shop asked Irwan to help them finish a build in time for the prestigious Yokohama Hot Rod Custom Show in Japan. As a thank you, they bought Irwan a plane ticket to accompany the bike to the show. Having just graduated with a degree in mechanical engineering, he was in shock.
“I was really, really blown away by the bikes I saw there,” he tells us. “The engineering, the complexity, the level of craftsmanship, the design. It was at that moment that I decided that this is what I wanted to do with my life, and that I had to come back here again, with my own bike, to show it to the world.”
Returning to the Mooneyes show became an obsession. “I followed the show every year on the website and social media. I studied the bikes that had won awards, the bikes that hadn’t, the shops that had won before but not that year, and the shops that hadn’t won before but did that year.”
The opportunity came when Malaysia’s largest custom show, Art of Speed, hosted an invitational event with a killer prize – a sponsored trip to show off your bike at Mooneyes. Before Irwan could scrape together all his savings to start a suitable project, the COVID-19 pandemic shut everything down.
It wasn’t until late last year that Art of Speed finally restarted the build. “This time, due to the lockdown and cost cutting, my financial situation was worse than last time,” Irwan tells us. “But I was determined.”
“I decided that this was the only chance in my life to realize this dream. I sold almost all my property and took out a personal loan from the bank to restart the project.”
Given how committed Irwan was to the project, the only option was to go all in. But before he set the grinder to work, he first studied every aspect of the design. “I tried to incorporate my superficial knowledge of motorcycle proportions; the golden ratio, the Fibonacci spiral, the synergy of lines, etc.”
“For example, the distance between the front edge of the rear wheel and the rear edge of the front wheel is equal to the distance from the center of the rear wheel to the front of the engine, the overall height of the motorcycle, and the length of the tank-seat unit. This number, multiplied by 1.618, is equal to the length from the front edge of the rear wheel to the center of the front wheel.”
Starting with the chassis, Irwan connected sections of tubing to a pair of steel plates that also serve as engine mounts. The plates were cut with an angle grinder and hand-drilled, taking inspiration from the crazy Kiyo's Garage three-engine land speeder.
There are more parallel lines in the frame design than you might imagine. Some are obvious, but others are much more subtle – like the way the exhaust flanges match the angle of the main down tube, and the way the top and bottom edges of the chainstays line up with the opposite edges of the frame plates.
A set of Yamaha RXZ forks supplied by Taikom Racing offer the only suspension on the bike. Irwan freed them from the brake and fender mounts, then cleaned up the lower sections until they were perfectly tubular. The forks are held in place by a pair of custom clamps with a very interesting design.
The lower triple clamp is where you'd expect it to be, but the upper triple clamp connects to the headset via a cutout in the frame journal. Irvan built it so that the top tube runs in a straight line from the upper triple clamp to the top of the rear tire.
To cut costs, Irwann built the wheels from as many recycled parts as possible. The 19-inch front rim and Pirelli tires are left over from previous projects, while the front hub is a modified part from a racing moped. Irwann removed the brake disc mounts and machined it to look more like a bicycle hub.
For the rear wheel, he took a spare tire from a car and cut out the center so he could attach it to the disc brake hub. Two Yamaha Y125Z calipers provide some stopping power.
The bike also has a unique twin-cylinder engine, a combination of two first-generation Yamaha RXZ 125 engines. “Believing that this bike could represent Malaysia in Japan, I chose the Yamaha RXZ 135 engine as the base. I can honestly say that the Yamaha RXZ is the most popular motorcycle in Malaysia; it has a cult-like following.”
Irvan had built a twin-engine Yamaha RXZ before, but that bike had one engine in front of the other. This time, he put them side by side, essentially creating a 180-degree inline twin. And since the first-generation RXZ was officially called the “Boss,” he called his creation the “Twinboss.”
Inside, the two separate crankshafts were modified to operate as a male-female pair. On the outside, the cases were separated and then welded together, then massaged until the whole thing looked like it had just rolled out of the Yamaha factory. “Even the Art of Speed judges weren’t impressed with the engine at first (because they thought it was stock),” says Irvan, “until I told them it was originally a single-cylinder engine and showed them photos of the modification process.”
“I was lucky because Taikom Racing and UMA Racing chipped in and supplied me with their parts, which was a big financial relief. 80 percent of the internal engine parts were from Taikom Racing, including the cylinder blocks, engine studs and bolts, seals, gaskets, reed valves, bearings, clutch assembly, stator coils and CDI. UMA Racing provided the carbs, ignition coils and engine oil.”
Much of the bike’s finishing kit is also custom-made. The exhaust system uses RXZ headers with chambers and hand-made mufflers. The handlebars are an old set that were modified and welded directly to the top triple clamp before being fitted with internal throttle and clutch controls. Irvan also made the foot controls, keeping them as minimal as possible.
Moving on to the bodywork, Irwan wanted an organic, one-piece unit that would “look sexy and have curves.” His friend at LNS Motor sponsored the paint job: the frame is chameleon brown, and the bodywork is black with a slight sheen. Azwan of Kedaung Leather Work finished off the Yamaha with vegetable-tanned buffalo leather detailing on the seat and grips.
Working only after hours and on a shoestring budget, Irwan threw everything he had into his Yamaha RXZ Twinboss. But when the Art of Speed show rolled around, it all paid off. Irwan took home the gold, securing his spot at this year’s Mooneyes.
“While people know FNG Works as a one-man show, there were a lot of people involved in this build – especially emotionally because they know my story, the challenges and the sacrifices.”
“There were a lot of tears when I was announced as the winner. Hopefully this bike will bring joy to more people when it is shown at the Yokohama Hot Rod Custom Show in December.”
Bravo, Irvan.
FNG works Instagram | Facebook | Images from Amin Hamid
Irvan would like to thank Taikom Racing, UMA Racing, LNS Motor, Kedaung Leather Work, Afiat Cap Gambus, Riders Garage, Bagiruang, Decibel Store and all the friends who contributed to help him complete this project.
