Building scooters is a somewhat funny business. You have overseas licensing conventions that force engine sizes into certain size brackets, and the displacement usually eases right up against the upper limits. (Ex: 149 cc in the 150 cc-or-lower bracket.) Things are a bit different in the U.S. market where the main consideration is whether the scoot is freeway/interstate legal or not, which requires that engine displacement be greater than 150 cc. Introducing the SMAX in 2016, Yamaha gave us the then newest freeway-legal scooter in its stable. An unusual engine size of 155 cc places the displacement just over the line making it legal to hit the interstate. Whichever the case, the SMAX serves as Yamaha’s current minimal-displacement highway commuter, second now in size to the new Xmax.

Design

“Last year, passenger comfort got a boost over the previous year’s model with increased padding in the pillion seat.”
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https://www.topspeed.com/motorcycles/motorcycle-reviews/yamaha/2016-2017-yamaha-smax-ar171238.html