X2 For what Sanddrag said. Get a larger engine - for 2 reasons.
1. The torque. Remember - Torque is what gets you up to that speed - Horsepower keeps you moving. I'd always go for more torque.
2. I'd personally don't feel very comfortable with an engine at 7,000+ RPMs doing only 30 mph down the road. Again - get the larger engine and you can gear it much better!
I don't know that much about the technicals on smaller engines - but it's still off the principle of a 2/4 stroke Internal Combustion engine...
And anyways - remember the saying - "There's no replacement for displacement"
