Remember Yamaha RXZ Twinboss twin cylinder two-stroke? Neither do we, because it never existed—except in the mind of Irwann Cheng.
The Malaysian custom builder, operating under the name FNG Works, has skillfully combined two Yamaha RXZ 135 engines with such finesse that you’d be forgiven for mistaking this for a factory unit. But what impressed us most about this homemade bike rickshaw It’s not its bespoke engine—nor its handcrafted chassis or its uncannily perfect proportions. What makes it special, though, is the epic journey Irwann undertook to bring it to life.
The seed was planted six years ago when another custom shop asked Irwann to help them finish their build in time for the prestigious Yokohama Hot Rod Show in Japan. As a thank you, they bought Irwann a plane ticket to fly the car to the show. Fresh from his mechanical engineering degree, he was blown away.
“I was really, really amazed by the bikes I saw there,” he told us. “The engineering, the complexity, the level of construction, the design. At that moment, I decided that this is what I wanted to do with my life, and I had to come back here again, with my own bike, to show it to the world.”
Going back to the Mooneyes show has become an obsession. “I follow the show every year from the website and social media channels. I study the bikes that won, the bikes that didn’t win, the workshops that won before but not that year, and the workshops that didn’t win before but won that year.”
An opportunity arose when Malaysia’s largest custom car show, Art of Speed, held a build-off competition with a huge prize—a sponsored trip to showcase their car at Mooneyes. Just as Irwann was scraping together his savings to launch a proper project, the COVID-19 pandemic shut everything down.
It was only late last year that Art of Speed restarted construction. “This time, due to the lockdown and staff cuts, my financial situation was worse than last time,” Irwann told us. “But I was committed.”
“I thought this was my only chance in life to pursue this dream. I sold most of my assets and took out a personal loan from the bank to restart the project.”
Given Irwann’s dedication to the project, going all-in was the only option. But before he even started, he tinkered with every aspect of the design. “I tried to incorporate my limited knowledge of motorcycle proportions; the golden ratio, Fibonacci spirals, line combinations, etc.”
“For example, the distance from the leading edge of the rear wheel to the trailing edge of the front wheel is equal to the distance from the center of the rear wheel to the front of the engine, the total height of the bike, and the length of the fuel tank. That number, multiplied by 1.618, is equal to the distance from the leading edge of the rear wheel to the center of the front wheel.”
Starting with the chassis, Irwann paired the tubing with a pair of steel plates that also served as engine mounts. The steel plates were cut with an angle grinder and drilled by hand, inspired by the madness of Kiyo’s Garage. triple engine acceleration.
Frame design has more parallel lines than you can shake a stick at. Some are obvious, but others are much more subtle—like the way the downtube flanges match the angle of the frame’s main downtube, and the way the top and bottom edges of the chain align with opposite edges of the frame plate.
A set of Yamaha RXZ forks, supplied by Taikom Racing, provide the sole suspension on the bike. Irwann freed them from the brake and fender mounts, then cleaned up the lower section until they were completely tubular. The forks are held in place by a pair of custom-made, interestingly designed forks.
The lower swingarm sits where you’d expect, but the upper swingarm connects to the steering column via a cutout in the frame neck. Irwann built it this way so the frame’s top tube can trace a straight line from the upper swingarm to the top of the rear tire.
To cut costs, Irwann cobbled together the wheels from as many recycled parts as possible. The 19” front rim and Pirelli tires were leftovers from previous projects, and the front axle was a modified racing motorcycle part. Irwann removed the brake disc mounts and machined them to look more like a bicycle axle.
For the rear wheel, he took a spare wheel from a car and cut the middle off so he could mount it to the disc brake hub. Two Yamaha Y125Z calipers provided decent stopping power.
And then there’s the bike’s unique twin-cylinder engine—a combination of two first-generation Yamaha RXZ 125 engines. “I thought this bike could represent Malaysia in Japan, so I chose the Yamaha RXZ 135 engine as the base. I can honestly say that the Yamaha RXZ is the most popular bike in Malaysia; it has a passionate fan base.”
Irwann had built a Yamaha RXZ twin before—but that bike had one engine positioned in front of the other. This time, he placed them side by side, creating a 180-degree inline twin. And since the first-generation RXZ was officially called the ‘Boss,’ he dubbed his creation the ‘Twinboss.’
Internally, two separate crankshafts have been modified to act as a male-female pair. Externally, the cases have been separated and then welded together, then massaged until the whole arrangement looks like it rolled straight out of the Yamaha factory. “Even the judges at Art of Speed weren’t impressed with the engine at first (thinking it was stock),” says Irwann, “until I told them it was originally a single-cylinder and showed them photos of the modification process.”
“I was lucky, because Taikom Racing and UMA Racing joined forces to supply me with parts—it was a huge financial boost. Eighty percent of the internals of the engine are from Taikom Racing, including the cylinder block, engine studs and bolts, oil seals, gaskets, valve leaves, bearings, clutch assembly, stator coils, and CDI. UMA Racing supplied the carburetors, ignition coils, and engine oil.”
Much of the bike’s finish is custom too. The exhaust system is an RXZ unit, with a hand-made muffler and chamber. The handlebars are an old unit that was modified and welded directly to the upper control arms, before being fitted with internal throttle and clutch controls. Irwann also made the foot controls, deliberately keeping them as minimal as possible.
Moving on to the bodywork, Irwann wanted an organic monocoque that “looked sexy and curvy”. His friends at LNS Motor provided the paint; Chameleon Brown for the frame and black with a subtle shimmer for the bodywork. Azwan from Kedaung Leather Work finished the Yamaha with vegetable tanned buffalo leather accents on the seat and grips.
Working only after normal business hours and operating on a shoestring budget, Irwann threw everything he had at his Yamaha RXZ Twinboss. But when the Art of Speed show rolled around, all the hard work paid off. Irwann took home the gold medal, securing his spot at this year’s Mooneyes show.
“Although people know FNG Works as a one-man company, there are many people who have been involved in this building process, especially emotionally, because they know my story, my struggles and my sacrifices.”
“Many people were in tears when I was announced as the winner. I hope this car will bring joy to many more people when it is displayed at the Yokohama Hot Rod Custom Show this December.”
Congratulations, Irwann.
FNG Project Instagram | Facebook | Image of Amin Hamid
Irwann wants to thank Taikom Racing, UMA Racing, LNS Motor, Kedaung Leather Work, Afiat Cap Gambus, Riders Garage, Bagiruang, Decibel Store and all friends who joined hands to help him complete this project.
