I've been looking into this. The cylinder is either nickel-carbide coated or nitride coated and can't be over bored. This is why Yamaha doesn't offer an over bore piston for rebuilds. There is also the issue of attempting to bore the cylinder block and running into the water jacket. jct842 stated above that the Majesty engine may work. It's work looking into if you're considering a big bore kit.
It's more gearing and how the CVT is set up that controls the power curve VS top speed. It may be possible to regear and lower rpm's at interstate speeds.
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