Triumph, of course, is known for its three-cylinder engines. After Hinckley tried to slug it out with the Japanese in the 600cc, four-cylinder supersport category, Triumph wised up and created the wonderful 675cc triple we know today. MV Agusta has recently joined the fray with its own 675cc triple.
Yamaha appears to be next in line. As we reported, Yamaha used INTERMOT to display a three-cylinder concept, and confirmed that at least one three-cylinder model will see production in the near future. As we pointed out in the same article, Yamaha has manufactured three-cylinder motorcycles in the past, including the XS750 and XS850 produced between 1976 and 1981. These bikes gained a good reputation for comfort and engine smoothness, and are still coveted by enthusiasts today. I found this web site dedicated to all things “Yamaha triple” that you may want to take a look at (it contains many interesting links and PDF files).