From the experts:

"The Yamaha SR400 has stood the test of time like no other model." “We decided to import the SR 400 in small quantities, based on the demand from tuners and special customers" says Product Planning manager Oliver Grill. Oliver expects the bike to remain exclusive. “The bike is of course not cheap with low production quantities, high-quality parts and production in Japan."
Total Motorcycle

"The 2015 Yamaha SR400...re-introduces a motorcycle that originally debuted in the U.S. in 1978. Not much beyond the addition of fuel injection has changed with the 399cc motorcycle, making this more like a classic reissue than a modern bike masquerading as old iron." "The SR400 is supremely manageable. Small, lightweight, and simple to operate, this naked bike recalls many of the things there are to like about back-to-basics motorcycles."
About.com

"Yamaha had been a little left out of the small bike market in North America, with nothing in between the ancient V-Star (a re-badged Virago) 250 and the 600cc sporty-but-comfortable FZ6R. Enter the SR400. Its looks can only be described as retro…so retro that owners will be fielding questions from strangers asking how long it took to restore it."
Ride Newfoundland, April 2014

"For many riders, the character, soul and image of a machine is far more important than its acceleration figures or potential lean angle. Fundamental qualities such as simplicity, ease of use and timeless design are more important to the SR400 owner. With its relaxed torque, light and agile chassis and sheer mechanical beauty, the SR400 is designed to appeal to riders looking for a motorcycle with a real heritage and character, and one which fully engages its owner."
MC News.com AU, April 2014

"The Yamaha SR500 sold in Australia from 1978 to 1982 and only a few thousand hit the streets. Since then, small volume importers have shipped in grey imports to satisfy the demand for SR bikes to customize into cafe racers." "Meanwhile, he can’t wipe the grin off his face as he trundles around the streets of Melbourne on the new Yamaha SR400. The fuel injection means it is not as hard to start, it idles smoothly and evenly, and it’s so easy to ride around town.” "The new model is a very sweet ride.”
Motorbike Writer, May 2014

"The Yamaha SR400 may very well be a time machine that can take us back to a more relaxed state of mind. A gentler and kinder world where we appreciate the sight of dragon flies and the smell of horses." "Yamaha says they plan to bring in 500 units."
Back Roads Motorcycle Rides, June 2014

"There is a lot to like about this cult classic, from its retro good looks to its easy handling personality, it has a carefree, other place and time kind of feel." "If you can get onboard with the anachronism of kickstarting a fuel-injected bike, you’ll find the 2015 Yamaha SR400 to be a satisfyingly enjoyable ride.
Ultimate Motorcycling, August 2014

"Real Retro? More Like, Real Survivor. "Overall, the SR400 is a fine little bike, mechanically sound and terrifically styled." "The SR is a fundamental motorcycle, and if you're after that essential vintage-bike look and feel without the constant upkeep, the SR400 may be the bike for you."
Motorcyclist, August 2014

"The motorcycle is quite literally a stamped-in-steel copy of the more than 30-year-old original." "Riders looking to relive the glory days or seeking an authentic classically-styled retro motorcycle, with a one-year warranty, will love the SR."
Motorcycle USA, August 2014

"Anyway, here the thing is, all 384 pounds of it, rolling on 18-inch wire wheels and tube-filled Bridgestone Battlax tires, for the low low price of $5,990. Yamaha’s people are throwing out phrases like mechanical honesty and elemental beauty to spin the SR, and they may be onto something.'"
Motorcycle.com. August 2014

"For any retro-loving motorcycle enthusiast, the eye glides along the sweet, svelte lines of the 2015 Yamaha SR400 just like it did in 1978. Because Yamaha got it right back then and correctly chose not to change much since. "And just think. Because it’s new there won’t be any stripped or rusted fasteners. That’s worth the $5990 asking price right there. Well, that and the satisfaction of kicking your motorcycle to life."
Cycle World. August 2014

"We haven’t seen this bike in 33 years on the U.S. market. Like a time capsule that’s been opened, the 2014 Yamaha SR400 is a completely new, old motorcycle." "It has all the charm and feelings of a vintage bike, without the repair bill." "You’re not going to keep up with your pal's 600, but you’ll be the one laughing while you wait on them at the bottom of the canyons or end of a traffic jam."
Ride Apart Inc. August 2014

"This Yamaha with its first introduction in the late 70s is still a serious motorcycle 35 years later." "With the growing desire for back-to-basics' Yamaha decided the time was ripe for a reintroduction." "The beauty of the SR is that the sympathetic-looking air cooler is not retro, but the real deal."
Motor magazine September 2014

"The 2015 Yamaha SR400 carries a retail price of $5,990, and is available in just one color, Liquid Graphite. Yamaha probably could have lowered the price by reducing the quality of some of the components, like the solid steel fenders and tank. I’m glad that they didn’t, because the SR400 feels like a solid piece of manufacturing."
Forbes September 2014

"The SR400 looks like the real deal because it is, a living classic that hasn’t changed much since it debuted nearly 40 years ago. I’ve watched guys stop to admire it in the parking lot, assessing its clean lines and generous chrome, wondering how old it is. And if they’re of a certain age, they pause, close their eyes briefly and think back to more carefree days. Those memories are priceless. Creating new ones will set you back $5,990."
Rider September 2014

Great article bob" I think we had only the SR500 back in the 70"s , , the XT road equivilent ,,,,

Great article bob" I think we had only the SR500 back in the 70"s , , the XT road equivilent ,,,,

The SR400 and SR500 were both introduced in 1978. After exports of the SR500 stopped to the US and Europe, it still continued to be sold in Japan. It was discontinued in 1999. The SR400 was sold in Japan only since 1978 for their licensing laws (restricting sales of bikes to younger riders to 400cc or less). After more than three decades, the SR400 is now being exported to Europe and the US in limited quantities.

SR400/SR500 notable differences

-SR400 has a lower compression ratio, a different crankshaft and a shorter piston stroke than the SR500 (the cylinder bore and piston are the same). Electronic fuel injection (w/required oxygen sensor) were added in 2010.

-SR500 used the same clutch as the XT/TT500 - SR400 has an easier effort clutch.

-SR400 has a modern front disc brake caliper and drilled rotor

-SR400 has a larger diameter silencer with catalytic converter

-The SR500 battery is located behind side cover. The SR400 battery is located under the seat (fuel pump located behind side cover)

-The SR400 has a softer, more comfortable seat (same bench shape)

-SR400 has a full rear chrome passenger grab rail

-SR400 has smaller, different design foot pegs

-some minor differences including side covers, mirrors, gauge housings & faces, turn signal lenses and reflectors.

There is a second and a half difference in the quarter mile time in favor of the SR500, which has 7 more hp. There is a 6 mpg increase in the fuel mileage in favor of the SR400 at 66 mpg, but testers keeping the bike under 65 miles per hour have recorded fuel mileage in the seventies.