Yamaha RX 100

Following the poor sales[2] of the Rajdoot 350, Yamaha needed to make a new product, and the recent success of Suzuki's AX 100 demonstrated the potential of small-capacity motorbikes in India.

In November 1985, Yamaha released the RX 100 to widespread acclaim. The appeal came largely from the high output of its 100 cc (6.1 cu in) engine. With its lightweight body and high power output, the resulting power to weight ratio of the bike made it the best 100 cc bike ever built for mass production, and as a result there is still a high demand for it many years after it ceased production.

A 1989 Modified Yamaha RX 100.

The RX 100 was quickly adopted by racers who recognized its potential for drag racing. Various modifications such as expansion chambers, head porting, engine tuning, sprocket changes and wheel size changes became fairly common. A large number of customization options include larger carburetors, air filters, quicker throttle, disc brakes, an additional 5th gear, race pistons, racing CDI systems, upgraded tires and suspension damping. Tuned RX 100's have completed a standing start quarter-mile in about 14 seconds – a respectable figure, considering the much larger BMW-S1000RR 4-Cylinder 1,000 cc (61 cu in) bike can cover one-quarter mile (0.4 km) in 10.2 seconds. The bikes were knock-down kits, produced in Japan and assembled in India. An easy differentiation between the Japanese and Indian market models was that the model produced in Japan had disc brakes, while the Indian market version had drum brakes front and rear.

Factory stock colors for the bikes were Peacock Blue, Cherry Red and Metallic Black. The only major change that the bike underwent was upgrading from a 6-volt electrical system to a 12-volt system in order to support a CDI (capacitor discharge ignition) system for improved ignition and timing. The RX 100 production lasted from November 1985 to March 1996. The tightening of emissions laws and regulations in India demanded lower emissions from these motorcycles, and as a result the RX 100 was replaced by the RX G.

The RX 100 model was replaced by the 11.8 bhp (8.8 kW), 132 cc (8.1 cu in) RXG, with a taller primary and secondary reduction. It had the same lightened flywheel from the RX 100 which caused unpleasantly abrupt acceleration. Yamaha replaced it with a heavier flywheel the following year. Then came the RX-Z in 1997, with a new chassis and shorter wheelbase, with the same primary reduction ratio as the RX100 but with a taller final reduction. The RX-Z was launched with sportier bodywork and produced 12 bhp (8.9 kW) at 6,500rpm. Following the RX-Z, the RX135 was launched in 1998 with the same engine as the RXZ but using the same chassis as the RX 100 or RXG. The RX135 saw a moderate success due to its refined power output and better fuel economy. In 2000 Yamaha launched the 14 bhp (10 kW), 7,500rpm RX135 5 speed with a large catalytic converter muffler (silencer). It's had a higher compression ratio and different port dimensions. It fared poorly in the India market due to its lower fuel economy, lack of marketing and quieter exhaust note which is departure from original rx series. It was discontinued after two years. The RX 135 5 speed was later recognized as the quickest RX-series bike and has a continued cult status due to its rarity. A 5-speed variant of the RX-Z with front disc brakes also had a limited release in 2001.

The final variant was a 4-speed RX 135 with a smaller catalytic converter silencer, classic rx100 like tank stripes and twin pod speedometer with white dials which was sold very briefly from 2003 to 2005.

The Yamaha RX 100 production run lasted from November 1985 to March 1996. The model was followed by the 132 cc RX G, which had a reduced 11.8 BHP. The RX G had an economy-minded engine configuration with the ports tuned to increase fuel-efficiency and decrease exhaust gas. This model was the reply to the stricter emissions controls, which were to continue affecting Yamaha's designs. The Japanese manufacturers responded in late 1997 with the Yamaha RX-135 and the RX-Z which had a tachometer and a sportier headlamp and body. Both were mechanically the same and the RX-135 received a lukewarm response. The market also saw five-speed versions of the RX-135s and RX-Z. The final variant was a four-speed RX 135 with a small type catalytic converter, sporting a fuel gauge and a speedometer with white dials which was sold very briefly in 2003–2005.

• Media related to Yamaha RX at Wikimedia Commons