28/07/2026
The principle was simple: if you can't make more power than the competition, weigh less. The Yamaha RD350LC made 49 HP from 347 cc. A Honda CB750 made 67 HP from 736 cc. A Kawasaki Z650 made 64 HP from 652 cc. On paper, the RD350 had no business being on the same road. In reality, the RD350LC weighed 340 pounds dry. The CB750 weighed 506 pounds. The Z650 weighed 467 pounds. Do the math: the RD350LC had a power-to-weight ratio of 0.144 HP per pound. The CB750 had 0.132. The Z650 had 0.137. The 347 cc two-stroke twin was faster on a power-to-weight basis than both 650 and 750 four-strokes. That's why they called it the giant killer.
The RD350 lineage started in 1973 with the air-cooled RD350 (39 HP, reed-valve induction, six-speed gearbox), grew to the RD400 in 1976 (44 HP from 399 cc, the last air-cooled RD sold in America), and evolved into the liquid-cooled RD350LC in 1980. The LC designation changed everything. Liquid cooling allowed tighter cylinder tolerances, higher sustained operating temperatures, and more aggressive port timing without the thermal distortion that air-cooled two-strokes suffered under load. Bore: 64 mm. Stroke: 54 mm. The same bore and stroke as the original 1973 RD350, but the liquid-cooled head and barrel transformed the engine's character. Peak power arrived at 8,000 RPM with a surge that two-stroke riders call "hitting the pipe" — the moment the exhaust expansion chamber reaches its resonant frequency and the engine suddenly doubles its effective output. Below the pipe, the RD350LC was mild. On the pipe, it was violent.
The RD350LC was never officially sold in the United States. The EPA's 1980 emissions regulations effectively killed large-displacement two-strokes in America. The RD400F Daytona (1979) was the last air-cooled RD available to US buyers. The liquid-cooled LC was sold in Canada, Europe, Japan, India, and Brazil. American enthusiasts who wanted one had to import from Canada or buy grey-market. This created a paradox: the most famous Yamaha RD was the one Americans couldn't buy. The forbidden fruit made it more desirable, not less. Today, imported RD350LCs command strong collector prices in the US precisely because they were never officially available.
The RD350 family's racing pedigree came directly from the Yamaha TZ350, the factory production racer that dominated the 350cc Grand Prix class through the 1970s. Same bore and stroke. Same parallel-twin two-stroke architecture. The TZ350 made 72 HP at 11,000 RPM in its final form, enough for 180 mph on a GP circuit. The RD350 was the street version: detuned, silenced, and fitted with lights and mirrors, but sharing the fundamental architecture that won world championships. Kenny Roberts, the first American to win the 500cc Grand Prix title (1978, 1979, 1980), learned to race on Yamaha two-strokes. The RD/RZ lineage continued through the YPVS power-valve models (1983-1986) and the RD500LC V4 (a street-legal replica of Roberts' YZR500 GP bike). Production in India continued until 1989. Brazilian production lasted until 1995. The two-stroke twin that was supposed to die with the emission regulations outlived every prediction. 347 cc. 49 HP. 340 pounds. Giant killer.
