Thump, thump, thump, thump, thump...

When the Model A Ford went on sale in 1928, replacing the Model T after 19 years of  production, Henry Ford remarked, "The only thing wrong with the Model T was that people stopped buying it." Yamaha doesn't have that problem. They introduced the SR500 in 1978, with an SR400 model in Japan to avoid the substantially higher taxes and licensing fees for bikes over 400cc. 32 years later, people are still buying it.

In the early 1970s, dirt bikes were all the rage, and four-stroke singles were the engine of choice. Simple, strong and light-weight, they were the ideal powerplant for the weekend warriors who wanted to have fun off-road. Yamaha was a leader in two-stroke engines, but they knew people preferred four-stokes. The XT500 they created as their entry into the four-stroke dirt-bike market was only their second four-stroke engine. But it was a good one. It was robust and powerful. Some bright egg in Iwata had the idea of making a street bike out of it to add another platform for the engine. The SR500 debuted in the fall of 1977 as a 1978 model.

It was a success. The bike's good looks were clearly influenced by the British thumpers of the 1960s, but with a look all it's own. Like the XT500 it was based on, there was no electric starter. You had to go through the process of kick-starting it. But once you knew how to do it, it was an easy bike to start. The SR500 was sold to export markets, and the SR400 was sold domestically in Japan. The SR500 was finally withdrawn from the US market in 1981, a victim of the American "bigger is better" mentality. But the bike continued to soldier on in the Japanese market.

As the years rolled on, a large aftermarket sprung up to help owners modify their bikes. You could by parts to turn it into a café racer or an American style dirt-tracker or to make it more dirt-capable or to make it into a touring bike or a WWII military despatch look-alike or any of a thousand other looks. All those customized bikes kept it in the forefront of motorcycling cool, which sustained sales year after year. Yamaha also made small changes to the bike to keep it fresh. Cast wheels were available early on. Disc brakes were replaced with drum brakes and a slightly smaller front wheel to evoke a more retro look in the mid-'80s. Dicsc came back in the mid-2000s. Paint schemes were constantly changed. But the bike has remained essentially unchanged.

Bikes don't stay in production for three decades unless there is something fundamentally right about it. The SR400 has all of the favorable traits of a road-going single with few of the drawbacks. It's light, easy  and fun to ride, handles well and has good looks that refuse to go out of style. It's reliable, doesn't leak oil and has only enough vibration in the engine to let you know you're not riding an inline-four.

32 years after it went on sale and 34 years after the engine was created, the bike is still being manufactured. Even today it's such an important part of Yamaha's lineup that they've created a website specially for the SR400, the SR400 Café. It's in Japanese, but it's full of all sorts of goodies, including images of every single color combination ever offered on the bike. Eventually, the bike will get fuel-injection to deal with more stringent emissions standards, but the old thumper will continue for as long as people keep buying it.