In Japan, 400cc bikes are popular because they classify as “medium” size; go bigger than 400cc and you’re in a more expensive tax class. But that line in the sand doesn’t apply in the U.S., so Suzuki gave its little twin a cc boost to make it more appealing to U.S. buyers. The Suzuki GS450 was really a 400 on steroids. Though it used the same format as the 1976-1979 GS400 and the interim GS425, the GS450 engine was new from the crank up.
Image courtesy Suzuki