1979 Yamaha RD400F Daytona Special

Intended to commemorate Yamaha’s racing success, the Yamaha RD400F Daytona Special ended up as a monument to the 2-stroke motorcycles that defined an era.

| July/August 2013

1979 Yamaha RD400F Daytona Special
Claimed power: 30hp @ 6,500rpm
Top speed: 98mph (period test)
Engine: 398 air-cooled 2-stroke parallel twin, 64mm x 54mm bore and stroke, 6.4:1 compression ratio
Weight (w/have tank fuel): 372lb (169kg) 
Fuel capacity/MPG: 4.6gal (40-50mpg)
Price then/now: $1,694/$3,000-$5,000

The Yamaha RD400F Daytona Special was the last hurrah of a long line of sporty midsized 2-strokes. Although Yamaha intended the Daytona to commemorate its racing successes of the previous year, this bike ended up as a monument to the 2-stoke motorcycles that defined an era. The Daytona Special was the last air-cooled street 2-stroke sold in the United States.

Once upon a time, the streets were full of inexpensive 2-stroke motorcycles. Mostly made in Japan, people either loved or hated these bikes. On the plus side, they were cheap to buy, generally easy to maintain, and typically went like stink. On the minus side, they fouled the air, made an offensive racket and often frightened people thanks to their noise and peaky power. Early ones had suspect handling and subpar brakes, but by the early Seventies the handling had improved and the brakes actually stopped the bike.

In 1973 Yamaha introduced the RD350, a 347cc 2-stroke twin that was loosely based on the then very successful Yamaha production racers. Carry-overs from the racers included the double cradle frame and much of the 2-stroke engine. Upgrades over prior Yamahas included a reed valve induction system and a front disc brake.

Yamaha engineers incorporated some interesting ideas into the powerplant, such as a small seventh port in the RD350’s induction system that fed directly from the carburetor manifold. The port provided an extra shot of fuel and air for improved combustion chamber filling and scavenging, and cooled the piston crown. As a result of the induction system — along with a well-supported, low friction crankshaft and a 6-speed transmission, the RD boasted a relatively wide powerband and a top speed just shy of 100mph. Most 2-strokes had powerbands the width of a guitar string, so the RD350 was a significant advance, making the RD a very civilized ride. The reed valve system also improved the gas mileage, another plus as 2-strokes were often very thirsty.

The RD350, although better than most of what was available, was not perfect. The front wheel had a tendency to become airborne under hard acceleration, the seat was uncomfortable after a few miles, and the oil tank leaked. But perfection was not required by the hordes of young RD fans — just speed, handling, acceleration and an affordable price, all of which the RD could deliver. Sales of RDs were brisk, and many turned up at local racetracks.

7/10/2013 4:26:28 PM

This is an interesting story about the RD400 Daytona but it has several errors. The horsepower is 43 at 7500 rpm and it is not the end of road legal air cooled 2-storkes in the US. Kawasaki sold the air cooled, oil injected, kick start KE100 until 2001 and Yamaha sold road legal small air cooled 2-stokes in the 80s and 90s. I am a fan of the 2-stroke stories as I ride a 1976 Kawasaki KH500 and 1971 Kawasaki A7SS on the street and all of my dirt and road race bikes are 2-stroke.

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