The Jap bikes with restrictors in them are not street legal bikes...
they are the biggest Honda 4-stroke, and the biggest Yamaha 4-stroke
these are supposed to be 'trailbikes'...(with headlight and taillight)
The other one is a now discontinued Suzuki 2-stroke trailbike,
(that was the one that came with the extra pipe)
Since they are not street legal I think the manuf's corked them up to be more
"socially responsible".... but they are also fairly easy to get street legal, and a lot of people uncork them anyway.... just like all the mopedders... everybody wants to go a little faster.
I have also heard of the UK "learner restricted" street legal bikes that they cork up so tight as to reduce a 30 HP bike down to 17HP... I believe they do that with intake and exhaust restrictors.