I made a little spreadsheet to check top speed in each gear, here's my 636:
[TABLE="width: 96"]
[TR]
[TD="class: xl65, width: 64, bgcolor: transparent, align: right"]1
[/TD]
[TD="class: xl66, width: 64, bgcolor: transparent, align: right"]112
[/TD]
[/TR]
[TR]
[TD="class: xl65, bgcolor: transparent, align: right"]2
[/TD]
[TD="class: xl66, bgcolor: transparent, align: right"]160
[/TD]
[/TR]
[TR]
[TD="class: xl65, bgcolor: transparent, align: right"]3
[/TD]
[TD="class: xl66, bgcolor: transparent, align: right"]197
[/TD]
[/TR]
[TR]
[TD="class: xl65, bgcolor: transparent, align: right"]4
[/TD]
[TD="class: xl66, bgcolor: transparent, align: right"]227
[/TD]
[/TR]
[TR]
[TD="class: xl65, bgcolor: transparent, align: right"]5
[/TD]
[TD="class: xl66, bgcolor: transparent, align: right"]258
[/TD]
[/TR]
[TR]
[TD="class: xl65, bgcolor: transparent, align: right"]6
[/TD]
[TD="class: xl66, bgcolor: transparent, align: right"]285
[/TD]
[/TR]
[/TABLE]
Rip 4 gears and you're nearly 230, I guess a liter bike would be even easier! An EX500 is not a bad one, although, you'll still be well into HTA in 4 gears...
[TABLE="width: 96"]
[TR]
[TD="class: xl65, width: 64, bgcolor: transparent, align: right"]1
[/TD]
[TD="class: xl66, width: 64, bgcolor: transparent, align: right"]72
[/TD]
[/TR]
[TR]
[TD="class: xl65, bgcolor: transparent, align: right"]2
[/TD]
[TD="class: xl66, bgcolor: transparent, align: right"]104
[/TD]
[/TR]
[TR]
[TD="class: xl65, bgcolor: transparent, align: right"]3
[/TD]
[TD="class: xl66, bgcolor: transparent, align: right"]134
[/TD]
[/TR]
[TR]
[TD="class: xl65, bgcolor: transparent, align: right"]4
[/TD]
[TD="class: xl66, bgcolor: transparent, align: right"]165
[/TD]
[/TR]
[TR]
[TD="class: xl65, bgcolor: transparent, align: right"]5
[/TD]
[TD="class: xl66, bgcolor: transparent, align: right"]193
[/TD]
[/TR]
[TR]
[TD="class: xl65, bgcolor: transparent, align: right"]6
[/TD]
[TD="class: xl66, bgcolor: transparent, align: right"]218
[/TD]
[/TR]
[/TABLE]
PS. I'm think 5/6 might be drag limited on this bike, I didn't really try but I hear 200kms is about the most people can get outta the bike.