Yamaha RD400 – Classic 70s Two Stroke Motorcycle

The Yamaha RD400 had a relatively short lifespan and was produced between 1976-1979 having been first introduced in the Summer of 1975. 

It followed on from the RD350 and was later replaced by the RD350LC in 1980 which took the world by storm as one of the leading two-stroke motorcycles of the 80s

The RD400 wasn’t just an over-bored RD350, the stroke was increased and this required Yamaha to produce new crankcases for the new model. 

It was a whole new machine produced to capitalise on the success of its predecessor while bringing something new to the table and it has become an icon within its own right. 

Let’s take a look at the Yamaha RD400 in a bit more detail.

Table of Contents

Yamaha RD400 Review

The RD400 was born into an era in the UK particularly where it was the Queen’s Silver Jubilee, pop music was running the charts and frankly the young and reckless were just a little bored with everything. 

Enter the Sex Pistols ushering in a wave of punk music and “Anarchy in the U.K.” 

Enter the Yamaha RD400 and what you have is a motorcycle to scratch the itch for young motorcyclists that want to replicate their rebellious lifestyles into their riding lives.

Yamaha RD400 was the first production motorcycle to feature cast wheels
The Yamaha RD400 was the first production motorcycle to feature cast wheels

The RD350 engine was copied as a base but new crankcases were produced and the engine was rubber mounted to reduce some of the vibrations that plagued the preceding model.

In an attempt to prevent the bike from pulling wheelies the engine was tilted forward to put more weight at the front. For many happy riders though this was simply an attempt and didn’t have its intended effect. 

The engine was highly delicate and sensitive in response to the throttle, so required a great deal of care from the rider to execute the right amount of throttle to gain the power desired. Too much and it could be a little overwhelming. 

The rev range on the new engine gets rushed through with a great deal of rapidity, there is no calm and collected acceleration to be found throughout any of the gears. 

One thing to note is that the engine is significantly quieter than the previous RD350 as Yamaha went out of their way to make it so. 

In order to do this the air box was increased in size to hold some of the noise down but allow a significant amount of airflow in order for the bike to perform well. 

New wheels and brakes also graced the Yamaha RD400. 

Unfortunately the single disc brakes on the front and rear were not up to much compared to the iconic acceleration that the RD400 came to be known for. 

The wheels on the other hand were significant as they were the first ever cast wheels on a production motorcycle and they became standard from the 1977 model. 

In terms of handling, the bike was great for darting into corners and pulling you back out of them. Precision steering and agility are two things the RD400 is known for. 

However, an RD400 with a nervous rider on board that is not too sure about their placement when leaning the bike over will suddenly become very jittery and unnerving. 

It is important to exercise as much care and precision into the riding of an RD at all speeds as feedback will soon be sent back to you if you are not confident in the movements you make. 

You have to concentrate to successfully navigate an RD400, it isn’t a bike that you can just sit back and cruise along, that isn’t where it wants to be or how it wants to be treated. 

It was a race developed machine and the ultimate racing street bike of its day. A street racer for all who dared. 

The Yamaha RD400 Daytona Special (400F) was built to be the last of the 400 series and was produced with the fact in mind that two-strokes were on their way out and as a result so was the RD series. 

Instead of just changing the paint schemes and a few revisions, the Daytona edition had enough modifications to make it a whole new machine that was a fitting tribute to all the RD’s that came before it.  

Other models included the RD400 C, E, D, and the final version F.

In 1979 the RD was fitted with a DCI unit, the cast wheels were made a little lighter and a new foot peg position along with some engine modifications. 

Cycle World tested the RD400C in 1976 and had this to say:

“The Yamaha RD400 C is the closest thing to a perfect motorcycle that we’ve ever run up against.”

Cycle Magazine wrote:

“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.”

Downsides

  • Rapid acceleration took its toll on the engine and engine wear was a known issue with owners. 
  • Crank seals were known to break.
  • Sixth gear was a constant source of problem for riders, notorious for wearing down.
  • Brakes were not really up to par to keep up with the rapid acceleration. 
  • Paintwork was a little sloppy. 

Yamaha RD400 Specifications

Engine and Transmission

  • Two-Stroke, Twin Cylinder, Reed-Valve, Tor que Induction
  • 398cc
  • Air-Cooled
  • Bore x Stroke – 64 x 64mm
  • Compression Ratio – 6.2:1
  • Induction – 2 x 28mm Mikuni Carburetors
  • Kick Start
  • Max Power – 44 horsepower at 7,500rpm
  • Max Torque – 41.1 Nm at 7,000rpm
  • Clutch – Wet Multiplate
  • Transmission – 6 Speed
  • Final Drive – Chain

Chassis and Dimensions

  • Front Suspension – Telescopic Forks
  • Rear Suspension – Swingarm with Dual Shocks
  • Front Brakes – Single 267mm Disc
  • Rear Brakes – Single Disc
  • Length – 1995mm
  • Width – 760mm
  • Height – 1060mm
  • Wheelbase – 1320mm
  • Seat Height – 800mm
  • Ground Clearance – 150mm
  • Dry Weight – 165.5kg
  • Wet Weight – 171kg
  • Fuel Capacity – 16.5 litres
Yamaha RD400 in blue

Yamaha RD400 top speed

The RD400 has a claimed top speed of around 109 mph, with 44 horsepower thumping out from the engine.

The quarter mile time was 14.01 seconds for the standard version. The Daytona special (400F), while not producing any additional ponies, covered the 1/4 mile in just under 14 seconds.

Yamaha RD400 value?

In the UK you will be looking at anywhere between £9,000-£12,500 for an RD400 in great condition. 

You may pay a little less for a bike that needs some work but you will likely pay around the same for a good quality restoration, such as this example that is priced at just under £10,000. 

The average price in the US is around $4,500-$7,000 so they do come up a little cheaper in the States than the UK. 

$6,200 will get you this 1976 model that is in pretty awesome condition.

Verdict

If you don’t want to pay out for an RD250LC or an RD350LC and are looking for something slightly calmer without losing the rebellious nature altogether, then the air cooled RD may be the exact vintage two-stroke you are looking for. 

The RD400 is a 1970s motorcycle with plenty of charm and will always be a head turner. It is also a bike that has plenty of usable power on the roads today, albeit it probably isn’t going to be your everyday bike but it is a really fun toy!

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