The mileage of RX100 varies between 30-40 kmpl and it cannot be increased due to the limitation of parts for the motorcycle. You can consider your RX100 as the best one if it returns 40 kmpl from its 2 stroke, 98 cc, single cylinder engine. The RX-100 was the only 100 cc motorcycle to touch a speed of 100 kmph and it came with excellent riding experience due to its lightweight body weighting just 95 kg when dry. It came with a 10.5 liter of fuel tank. The engine of the RX-100 is good enough to produce 11 BHP @ 7,500 rpm and 10.39 NM @ 6,500 rpm. It came with drum brakes only, making it quiet unsafe for high speed riding. You can consult a mechanic for a carburettor swap from some other bike but that would end the real identity of the RX-100.

All You Need to Know about the Legendary Yamaha RX 100