Retrospective: Yamaha DT400 Enduro: 1975 – 1979

Test riders loved this new big-bore 400cc enduro. Go just about anywhere, do just about anything and do it with zip! The DT1 250 had grown up, first to 360 size, and now 400, and had become an extremely seductive machine.

Weighing less than 300 pounds, with equal amounts of horsepower and torque, the oversquare single-cylinder two-stroke could tackle a dune in the Mojave Desert, climb gnarly trails high in the Rocky Mountains or hare along old logging roads in Maine.

These magazine riders were pretty darned experienced, and enjoyed pinning the throttle, fore and aft, making maximum use of the power at all times. However, when it came down to puttering along rural roads, the 400’s engine was not quite as smooth as many relaxed riders would have liked—good for the hurly-burly of competition, or the adrenalin-seeking individual off on his own, not so comfy for the commuter crowd.

1975 Yamaha DT400 Enduro.
1975 Yamaha DT400 Enduro.

We should go back to the beginning, which was that excellent DT1 250 of 1968. The Japanese had finally realized that there was a specific “American” market, which did not exist in Japan or Europe—and it was those riders who wanted to make use of our vast publicly owned wilderness, and do it at a pace that could give a minor rise to the adrenalin level. The misnamed “street scramblers” were just not suitable, being way too street oriented and not nearly scramblerish enough. One of the real blessings of this great land of ours are those huge expanses of unoccupied land, and all that was needed was a properly set up motorcycle to enjoy the tens of thousands of miles of dirt roads and trails…and a big gas tank was very useful, too.

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The DT1 was a superb motorcycle right off the drawing board, as its two-stroke, piston-port single with five ports provided the good lowend grunt that play-bikers wanted. Yamaha realized that there was a big difference between a machine that could win races and a machine that a noncompetitive rider would enjoy.

1975 Yamaha DT400 Enduro.
1975 Yamaha DT400 Enduro.

This unitized powerplant was bolted into a cradle frame using a double loop, plenty strong enough to cope with the claimed 22 horsepower. It was great fun without being too finicky. And just in case somebody wanted to race it, a Genuine Yamaha Tuning kit with a new cylinder, piston, expansion chamber, etc., was available as well.

Dealers could not keep them in stock. And the competitive MX and YZ models that followed were eagerly snapped up by racers. As was the smaller 125cc AT1 Enduro that soon followed, and, in 1970, the bigger 351cc RT1 360 Enduro with a bore of 80mm, stroke, 70mm. Then in 1974 the RT1 was modified and reintroduced as the DT360A Enduro, the Yamaha marketing types realizing that the success of the original DT1 250 gave value to those DT letters. The DT360A used a lot of MX parts, including the chassis, to give it both sportier handling and more power. Also new was the reed-valve induction system and CDI ignition, which did away with the oft-times bothersome points.

1975 Yamaha DT400 Enduro.
1975 Yamaha DT400 Enduro.

But the DT360A was a one-year only machine, as Yamaha soon realized that there had not been enough differentiation from the previous RT—so lo and behold, in 1975 the DT400B appeared, the 360A having been bored out to 85mm for a total of 397cc. It was crowned with a very sexy new head with radial finning. The Mikuni carburetor was the 32mm size, and with the reed valves this made for a rather thirsty engine, getting only 30 mpg or less when honking down a sand wash—and the smallish gas tank only held 2.4 gallons. That certainly restricted the range, even though the oil tank for the automatic lubrication held 1.6 quarts, and was good for two full gas tanks.

Primary power went through helical gears to the multiplate clutch, and then into the five-speed transmission. At the rear wheel the dyno measured almost 24 horsepower at 5,500 rpm, and 24 lb-ft of torque at 5,000 rpm. Happiness for the experienced rider was best found at 5,000 rpm, and in fifth gear on a straight stretch of road the bike could happily exceed 80 mph.

However, with a steepish rake of 30 degrees, and 5.1 inches of trail, such speeds were not pursued for long. The fork used progressive springing with three stages; the Thermo-Flow shocks at the rear had double springs and remote reservoirs. A 3.00 x 21 Dunlop Trials tire was on the front, a 4.00 x 18 on the back…though a 4.50 knobby could be squeezed in. The single-leading-shoe brakes were intended for dirt riding, and could cause a mild panic when attempting a fast, unplanned stop on the pavement. The wheelbase was 56 inches.

1975 Yamaha DT400 Enduro.
1975 Yamaha DT400 Enduro.

The biggest problem was in starting the bike. A 400cc single two-stroke is a hefty engine to get fired, and while the automatic compression release worked like a charm, the CDI could be less cooperative when starting off first thing in the morning. Also, when the engine was hot, a rider could spend a lot of energy kicking. As one magazine put it, there was no sure-fire drill that could be followed, and starting lacked any predictability.

Once running, the DT400 was a trifle lurchy on the road, as the engine did not really take kindly to a constant throttle—unless it was constantly wide open. On first look, dealers thought they would sell these bikes by the thousands, even at $1,370. However, a year later the noncurrent 1975 models were on sale for $948. Even with the less-than-expected sales, Yamaha went on improving the DT400, making the rear suspension a mono-shocker for 1977.

1975 Yamaha DT400 Enduro.
1975 Yamaha DT400 Enduro.

Yamaha was also trying to enlarge the market for these big-bore twostrokes, offering a race version YZ400, and for 1976 they put lights and a muffler on the YZ and presented it as a serious enduro model, the IT400, trying to compete with the European ISDT models. But the two-stroke era was coming to an end, and Yamaha knew it.

Which is why in 1976 Yamaha introduced a 500cc four-stroke single in the road-legal XT and off-road TT versions. The DT400 was kept on the payroll until 1979, and then retired.

(This Retrospective article was published in the February 2010 issue of Rider magazine.)

37 COMMENTS

  1. I bought a 1977 dt400 off a buddy last year, it’s not perfect but it is fairly clean for it’s age, all original. What would a bike like this be worth (ballpark)….it runs good, has a little piston slap, probably could use a top end rebuild.

    Thanks

    Tom.

  2. I have a 1976 DT400 that I’ve been riding. Starting when hot is usually pretty easy and mostly just needs one kick. From cold it needs choke until it fires once, then choke off and kick it until it runs, which sometimes can be more than I would like. But it always starts. And yes 30mph through a town is tough and annoying. In some cases the best technique is to accelerate hard then pull in the clutch and coast up to the traffic ahead. As long as your pulling a slight load it’s not so bad. Front end has a light feel to it, but overall for 1976 it’s a pretty nice machine and it beats walking through the woods by a lot.

    • I am looking for a driving job with about 5 years left to work. I like working by myself and have my cdl. I have experience driving 20 and 24’ box trucks. Any job for consideration would be appreciated. Thank you.

  3. Hi guys,
    I am about to pick up a DT 400 but not sure which year it is, either 75 or 76. Where can I find S/N listings ? It starts 501-
    If anyone is interested this will be cleaned up and running well and for sale.
    No title but you may not want to come to Ontario, Canada to get it ??
    What should I look out for when I look at it ?
    Thanks everyone,
    Flint

  4. HI guys. I have a DT400E i bought a carburetor for it and now i install it. But am still trying to make out which side of the carb is the right side for the oil pump line. Can anyone help me out?

    • It should be a hole on the right side front of the mik uni carburetor it should have a small brass pipe that the hose from the oil pump hooks to, which is also on the right side.

    • The oil line comes from pump under the pump cover on clutch or right side of the engine to right side of carb. Right side as being your right leg side.

  5. I PUT AROUND 10,000 MILES A YEAR BETWEEN 2 78 DT 400s FROM 1985 TO 1992 WHEN I LIVED IN SIMI VALLEY CA. ON AND OFF ROAD. THE SERIAL NUMBERS WERE 11 APART AND MOST LIKELY CAME FROM SIMI VALLEY CYCLES, ONE WOULD OUT RUN A MUSTANG GT FROM STOPLIGHT TO STOPLIGHT AND DESTROY HELLS ANGELS HARLEYS IN A DRAGRACE. GO WIDE OPEN AROUND 95MPH MANY MORNINGS WESTBOUND ON THE 118 FREEWAY WHEN COMMUTING FROM SIMI TO MOORPARK. TEAR THEM DOWN AND CHECK THE TOP END TOLERENCES AROUND EVERY 5000 MILES AND USE GOOD OIL AND FUEL. 90 TO 92 OCTANE WORKS BEST. HAVE FUN

  6. I have a 1976 in storage, I bought new when I was 17 years old. I have other motorcycles since but this bad boy would climb the highest sand hill, go through mud and water above the muffler (keep it running of course), climbed 100 steps of a High School, go 75 mph down a beach, you name it. It was not a cruiser. Has lights just to make it street legal. I can not even remember how many wild places I have been with it. Not one problem ever!
    Yet, only 3,500 miles, original sprocket, chain, tires, everything. This bike, I promise’ from 0 to 60, would leave the baddest street bike in the dust. I used to “sand ballet”; crouch up in soft long sand field and in 3rd gear, drift ( not a term back then) side to side like snow skiing. People on the road beside this sand pit would stop and watch. Never once did this rocket bog down even in higher gears.
    Loved to put my hot girlfriend on the back and terrorize the beach, where I live.
    It has been sitting for years and I am giving it to my high school Buddy, whose Father sold me this bike for $1,000 (on time) when I needed transportation to go to local college. He will refurbish it and I will ride it once again soon ( likely on the back wheel)👍
    Cory Gore
    Wrightsville Beach, NC

  7. I have a 1976 Yamaha DT 400 refurbished with OEM parts, except handle bars and chain adjusters. Runs extremely well with less than 6,000 miles. I have manuals, parts and a desire to sell. I am located in Saratoga Springs, NY.

    • Hi Bill, would you have some pic,s of it, and how much would you take for the bike.I had one but it needed to much work, repair,s ect..I all so live in winnipeg, Manitoba , Canada AND WOULD NEED TO HAVE IT SHIPPED SOME HOW. LOVED THE BIKE. I would love to own another one if the price is right.Thanks Bill.

      • Absolutely interested in this bike. Do you still have it and how much are you asking. I live in Maryland and would come and get it if we can make a deal.

  8. I have a Yamaha 400 DT 1976. Been cleaning it up a bit. Anyone know where I can find a good replacement seat? The rain and vinyl is pretty warn.

  9. Bill be in Saratoga springs New York do you still have your motorcycle? Is it running good? And how much do you want for it?

  10. I have a 75 DT 400 with 3500 miles for sale in Frankenmuth, MI.
    Rebuilt with Wiseco piston within last 200 miles. Ran great last time I rode.
    Custom front and rear fenders, flexible rear turn signals from later DT, and rear knobby.
    Has one dent on left side of gas tank. Needs new front tire and battery.
    Make Offer

  11. I have a 1979 Yamaha DT400F, Canadian model with 1500km on it. Mint with US title. I bought it from a fellow up in Yonkers , New York a couple of years ago. It is all original -Sunshine red- and runs great too. I have a ’79 Canadian Yamaha brochure for it just to show proof there was such an animal. The last year of the Yamaha DT400E here in the US was 1978. The last year of the Yamaha DT250F was 1979 here in the US. This is original, complete, running, and EXTREMELY RARE!!! What could this be worth??? Has anyone else ever seen one??? This is the prize of my collection I have acquired over the past 25 years collecting vintage bikes and in not for sale at this time.

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