The Modenas KR3 (later known as the Proton KR3) was a racing motorcycle made by the Malaysian motorcycle company Modenas. The bike was used in the 500cc class of grand Prix motorcycle racing from 1997 until 2001, when the company got taken over by the Malaysian automobile company Proton. Proton renamed the bike, calling it the Proton KR3 and using it for three more seasons - from 2002 to 2004 - before replacing it with the newer Proton KR5 machine.
History
The origins of the KR3 lie with the strained relationship three-time 500cc champion Kenny Roberts had with the Factory Yamaha team at the time. After Wayne Rainey became paralysed from the chest down due to a crash he sustained at the 1993 Italian Grand Prix and Yamaha's rivals Honda and Mick Doohan took multiple titles, Roberts became increasingly unhappy with Yamaha's working method in the mid 1990s. He was constantly unhappy with the progress of their bikes and even complained many times publicly that the factory did not listen to his feedback on how to improve their motorcycles.
Because of this, he made an announcement that surprised everyone in 1996 – he was breaking away from the Factory Yamaha team - after 25 years of close collaboration - at the end of the 1996 season, working together with the Modenas company to create a new motorcycle for the newly formed Team Roberts in 1997. The main reasons why Modenas decided to work together with Roberts was for two reasons: The company hoped that some of the technology would eventually make their way into their future models, and that participation in the 500cc would make their brand more known amongst the public.
The KR team decided to move the base of operations to the "Motorsport Valley" in the United Kingdom where some Formula 1 and race car teams are based and began working together with Tom Walkinshaw Racing (TWR).
They decided to create a unique three-cylinder, two-stroke, 500cc machine since the rules at the time gave three-cylinder machines a 10kg weight advantage over the usual four-cylinder bikes. The idea was that the lower weight allowed the bike to be more agile and carry more speed mid-corner. This was also deemed as an advantage as the racetracks during this time had more corners than long straights for the four-cylinder machines to utilize, some examples being Shah Alam and Donington Park. However, they also were aware that a three-cylinder bike would make less horsepower compared to a four-cylinder one. To solve this problem, the team focused on improving volumetric efficiency (how much fuel-air mixture the engine could induct).
The engine design was supervised by Bud Askland, the father of the team's manager Chuck Askland. They created a 498cc engine with "square" dimensions i.e. same bore and stroke figures of 59.6 mm x 59.6 mm. The Vee-angle between the cylinders was set at nearly 180o with two cylinders down below and one up top. The frame was designed to give the bike better handling characteristics. The KR team worked with TWR and French chassis maker FTR, which resulted in an aluminium twin-spar "deltabox" frame that's smaller and lighter than conventional Japanese designs at the time. The headstock featured eccentric carriers which would allow adjustments of the steering's rake angle and trail. There were also eccentric carriers in the swingarm mount which were created to adjust the height of the swingarm pivot. These were completely new and unheard of at the time. Even the fueling system was ahead of its time, the team adopting electronic carburetors without float bowls which used ducted air to atomize the fuel, much like a fuel-injection system. KR hoped that such a setup would avoid the fuel from emulsifying from intense vibrations. Arrow made an exhaust system for the engine. The result of this was an engine that produced 160 hp in the early years, and the team went on to improve the engine, producing 180 hp in 2002. The bodywork was designed in such a way that it would wrap tightly around the frame for a smaller frontal profile. Consequently, the radiator was moved to under the seat where ducts supplied cooling air to it.