Duke of Oil: 1976 Yamaha RD400C

The Yamaha RD400 is an even better version of America’s previous favorite 2-stroke motorcycle, the RD350.

| November/December 2018

  • classic Yamaha motorcycles
    1976 Yamaha RD400C.
    Photo by Dain Gingerelli
  • classic Yamaha motorcycles
    1976 Yamaha RD400C.
    Photo by Dain Gingerelli
  • classic Yamaha motorcycles
    1976 Yamaha RD400C.
    Photo by Dain Gingerelli
  • classic Yamaha motorcycles
    1976 Yamaha RD400C.
    Photo by Dain Gingerelli
  • classic Yamaha motorcycles
    The 399cc air-cooled 2-stroke twin made just more than 35 horsepower on the Cycle dyno.
    Photo by Dain Gingerelli
  • classic Yamaha motorcycles
    The 399cc air-cooled 2-stroke twin made just more than 35 horsepower on the Cycle dyno.
    Photo by Dain Gingerelli
  • classic Yamaha motorcycles
    1976 Yamaha RD400C.
    Photo by Dain Gingerelli
  • classic Yamaha motorcycles
    The solid cast aluminum wheels were among the first cast wheels on a production motorcycle.
    Photo by Dain Gingerelli
  • classic Yamaha motorcycles
    The solid cast aluminum wheels were among the first cast wheels on a production motorcycle.
    Photo by Dain Gingerelli
  • classic Yamaha motorcycles
    1976 Yamaha RD400C.
    Photo by Dain Gingerelli
  • classic Yamaha motorcycles
    1976 Yamaha RD400C.
    Photo by Dain GIngerelli

  • classic Yamaha motorcycles
  • classic Yamaha motorcycles
  • classic Yamaha motorcycles
  • classic Yamaha motorcycles
  • classic Yamaha motorcycles
  • classic Yamaha motorcycles
  • classic Yamaha motorcycles
  • classic Yamaha motorcycles
  • classic Yamaha motorcycles
  • classic Yamaha motorcycles
  • classic Yamaha motorcycles

1976 Yamaha RD400C

  • Engine: 399cc air-cooled 2-stroke parallel twin, 64mm x 62mm bore and stroke, 6.2:1 compression ratio, 35.48hp @ 7,000rpm (rear wheel, Cycle dyno)
  • Top speed: 95mph (period test)
  • Carburetion: Two 28mm Mikuni w/Yamaha Autolube oil injection
  • Transmission: 6-speed, chain final drive
  • Electrics: 12v, coil and breaker points ignition
  • Frame/wheelbase: Dual downtube twin-loop frame/53in (1,346mm)
  • Suspension: Telescopic fork front, dual shocks w/adjustable preload rear
  • Brakes: 10.4in (264mm) discs front and rear
  • Tires: 3.25 x 18in front, 3.5 x 18in rear
  • Weight (wet): 377lb (171kg)
  • Seat height: 33in (838mm)
  • Fuel capacity/MPG: 3.4gal (12.9ltr)/45mpg (period test)
  • Price then/now: $1,219/$2,500-$9,000

Yamaha's plan to update its popular 1975 RD350B model was simple: For model year 1976 they committed to building an even better version of America's favorite 2-stroke motorcycle.

The solution was found in upping the little oil-burner's capacity, which Yamaha engineers did by about 14 percent, stretching the stroke from 54mm to 62mm for a boost from 347cc to a full 399cc. The end result was the RD400C, perhaps the most advanced production 2-stroke motorcycle up to that time.

But the bigger-is-better philosophy was only the tip of the iceberg, as that bigger engine formed the foundation for a much improved street bike. To borrow from Cycle World magazine's test in their March 1976 issue: "The Yamaha RD400C is the closest thing to a perfect motorcycle that we've ever run up against. As a matter of fact, there is only one item that keeps it from being the world's first perfect motorcycle, but we won't tell you what it is... at least not until we've told you about the rest of this beauty."

If CW's words come across as excessive hyperbole, consider Cycle magazine's lead-in to its road test the following month: "The quickest, fastest, best-handling, and hardest-braking lightweight ever now joins the engine capacity creep and gets more comfortable without giving up as the world's best, and only, midi-Superbike."



So what prompted the two leading motorcycle publications of the era to treat this mid-displacement roadster like royalty? Let's put Drew Immiti's sparkling original jewel (his RD400C boasts original paint, chrome and seat upholstery) on its centerstand for a close walk-around of what Yamaha offered 42 years ago.

First things first

Deciding which to examine first, the engine or the chassis, is tough, because as Cycle World stated, this bike borders on perfection. But since most (if not all) of us are gear heads, let's start with that blacked-out, air-cooled, 2-stroke engine, which was more than just a stroked-out 350. It was practically an all-new engine.



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