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Yamaha Road Racers

WHAT ARE THESE MOTORCYCLES? These bikes were built as production road racing motorcycles, for race track use only. For this reason they lack such things as head- and taillights and do not have kick- or electric starters. These were built at the end of the great motorcycle boom decade of the 1970s, when hundreds of Yamaha production racers were bought by both amateur and professional racers.

The concept of a production racer originated before WW II, when makers like Norton and Velocette offered for sale “TT replicas” – racing motorcycles closely similar to the factory racers fielded by those factories in the classic Isle of Man TT races. After WW II most non-factory riders rode such bikes, but their manufacture ended in 1962-3, as the BSA Gold Star, Matchless G-50, and Manx Norton models were discontinued by their makers.

Existing classic four-stroke singles raced on for another decade, but their growing obsolescence created a production racer “vacuum”.

WHY DID YAMAHA BUILD PRODUCTION RACERS? Like 200 other Japanese companies of the early 1950s, Yamaha produced small motorcycles to satisfy postwar demand for cheap transportation. When they flourished and survived, they sought foreign markets. Could they complete with established motorcycle brands abroad? Like Honda and Suzuki, Yamaha decided to establish their name through success in European Grand Prix racing. They also knew the power of the US market, so they created two racing departments – one to design and build specialized machines for European Grand Prix, and the other to modify production models to race under American Motorcyclist Association (AMA) rules in the US.

The first of these Yamaha production racers to achieve real success was the air-cooled TD1-B of 1965, powered by a simple 250-cc two-stroke whose two cylinders were side-by-side. The retail price was $1147.00. Such machines – mostly in the hands of “privateers” (non-factory-supported riders) – soon dominated the AMA’s 250 class by defeating existing four-strokes – the Harley-Davidson Aer Macchis and Ducatis.

WHY WERE THESE BIKES POPULAR? American motorcycle racing was based on production bikes, modified for competition. Yet such modification became increasingly specialized, requiring knowledge and equipment. Yamaha, by offering race-ready machines, attracted many buyers.

Unlike the four-stroke engines that power cars and trucks, these two-stroke engines had no mechanical valves, and so could be made at lower cost. Because a two-stroke engine’s cylinders fire once every revolution of the crank, rather than every other revolution as in four-strokes, its pistons are heated by combustion twice as often. This works if the engine is tuned correctly, but if not, excessive heat could expand a piston enough to make it seize in its cylinder. This was the price of simplicity. Yet in 30 minutes of trackside work, a racer could replace the seized piston at low cost and be ready to ride. A clutch could be serviced in 20 minutes and even a crankshaft could be changed in an hour. Yamaha 250s therefore launched many a distinguished career in professional racing.

In 1968 Yamaha added a 350-cc production racer which was immediately competitive with most 500 and 750cc four-strokes. The 350, in its 1972 form, was nearly 100 pounds lighter than its four-stroke rivals, and their equal in power-to-weight ratio. Yamaha 350 production racers won the prestigious Daytona 200-mile race in both 1972 and 1973, defeating 750-cc four-stroke motorcycles from traditional British and American makers. Two-strokes then ruled in AMA racing until 1984.

ALL CHANGE IN 1968 New racing rules from the European FIM banned most of the super-expensive factory Grand Prix bikes of the 1960s, so Yamaha production racers, originally designed for the US, now went GP racing as well. That is why you see here both a TZ125 and a TZ500, built especially for European GP classes not supported in the US.

After a quarter-century of two-stroke dominance in European GP racing, the last two-stroke road racing class (125-cc) ended in 2011. Both US and GP racing are 100% four-stroke-powered today.

WHY ARE THESE ENGINES WATER-COOLED? Motorcycle engines were air-cooled for many years, and older riders even today like the look of cooling fins. However, as Yamaha’s 250 production racers were developed to give more power every year, a point was reached beyond which air cooling could no longer prevent overheating. For that reason the machines you see here have radiators (mounted between the engine and front wheel) and water pumps. Cooling fins have been replaced by featureless water-jackets.

YAMAHA PRODUCTION ROAD RACERS? In 1972 Suzuki and Kawasaki brought 100-horsepower two-stroke triples to the Daytona races. Their power and 175-mph speeds destroyed the best available tires and showed that chassis and suspension technologies were just as inadequate. This crisis forced development of wide, round-section slick tires, single-shock rear suspension, and stiffer chassis. Yamaha’s TZ750 four-cylinder bike appeared in 1974, and with continuing development was able to win the Daytona 200 for nine successive years.

Emissions regulations put an end to production of two-stroke street bikes in the 1980-84 period, but when light weight, high-performance liquid-cooled four-stroke engines came into being in the 1990s, the improved tires, suspension, and chassis technologies intensively developed in the two-stroke era were ready to carry them into the 21st century.

 yamama tz125TZ125G (1980)

  • Engine; two-stroke water-cooled, 1 cylinder, bore and stroke 56 X 50 = 123.1-cc (7.5 cubic-inches), 6-speed transmission.
  • Power; 30-hp @ 12,000-rpm (4.0 horsepower per cubic inch)
  • Equipment; Hitachi CDI (electronic) ignition, Mikuni VM34 carburetor
  • Chassis wheelbase 47.4”
  • Weight (dry) 158-lb

 

tz250TZ250G (1980)

  • Engine; two-stroke water-cooled, 2 cylinders, bore and stroke 54.25 X 54-mm = 249.6-cc (15.2 cubic inches), 6-speed transmission.
  • Power; 55-hp @11,500-rpm (3.6 horsepower per cubic inch)
  • Equipment; Hitachi CDI (electronic) ignition, 2 Mikuni VM34 carburetors
  • Chassis wheelbase 51.8”
  • Weight (dry) 235-lb

 

tz 350TZ350G (1980)

  • Engine; two-stroke water-cooled, 2 cylinders, bore and stroke 64 X 54-mm = 347.4-cc (21.2 cubic inches), 6-speed transmission.
  • Power; 72-hp @ 10,500 (could in expert hands be modified to ~ 80-hp) (3.4 horsepower per cubic inch)
  • Equipment; Hitachi CDI (electronic) ignition, 2 Mikuni VM38 carburetors.
  • Chassis wheelbase 52.0”
  • Weight (dry) 240-lb.

 

tz 500TZ500 (1980)

  • Engine: two-stroke water-cooled 4-cylinder, bore and stroke 56 X 50.5 = 497.5-cc (30.4 cubic inches), 6-speed transmission
  • Power; more than 110-hp @ 12,000-rpm (factory engines made as much as 125-hp)
  • Equipment; Hitachi advance-retard CDI (electronic) ignition, four Mikuni VM34 carburetors
  • Chassis wheelbase; 54”
  • Weight (dry) 306-lb

 

yahama tz750

TZ750G (1980)

  • Engine; two-stroke water-cooled, 4 cylinders, bore and stroke 66.4 X 54-mm = 748.0-cc (45.7 cubic inches), 6-speed transmission.
  • Power; 120-hp @ 10,500-rpm (2.6 horsepower per cubic inch)
  • Equipment; Hitachi CDI (electronic) ignition, 4 Mikuni VM34 carburetors.
  • Chassis wheelbase 56”
  • Weight (dry) 325-lb.

Photos © of P3 Image Studios – James A. Harding