G,
I have a Reflex 250 ABS that I use everyday for the commute. Being the slipperiest of the 250/400 big-scoots, it has a top speed similar to the AN400 (
[email protected] 9,000rpm) as long as you are a size and shape that fits inside the air bubble created by the front cowl. I used this as an alternative to the X11 as a wet weather tourer for 18 months before buying the 650. Granted it couldn’t go up hills, but it went down them very quickly indeed, and cruised all day at 60mph without problem with passenger. Solo, you can cruise at 70mph all day without any problem at all. Acceleration from 70mph to the 83mph top speed is similar to a 1litre 5 door runabout – hardly urgent.
The AN400 has a true top-speed of around 85-90mph (depending on your size and shape) but it can cruise all day at 70mph, but I suspect that this is not the purpose that it was designed for.
The single cylinder scooters are still designed largely for the Japanese market in mind, and with the global market as a distinct number 2. Have you ever thought why the Japanese manufacturers produce 400cc singles as opposed to 500cc singles like the Italians? It's to conform to the Japanese license categories (250/400/unlimited). These things are made for Japan – and largely Tokyo - where they replace the car for many inhabitants and have killed the 400cc conventional bike market dead. No longer does a Japanese highschool boy pass his 400cc bike test at 16 and jump onto a loud-piped CB400, uniformed girlfriend's legs on full view as her pleated skirt flies up in the wind. No, no. Now it's a neon-underlit 2005 Forza 250 with built in speakers blasting J-Pop over the rumble of his straight through pipe as he pumps the throttle pointlessly, whislt holding the rear brake, at junctions. It's also the choice for many business people tired of being squashed to death each morning on the subway.
The 250/400cc big-scoots are designed to give strong performance around town, combined with ease of riding in all weather conditions, good ergonomics for rider and passenger (for people between 5ft and 5ft 10ins), carrying space good for two full sized helmets / A4 briefcase / golf clubs / camping gear / tennis gear, and the ability to go for short touring (possibly overnight camping running up 300 miles or so). Dedicated 75mph highway cruising is not specifically what they are designed for – the highway speed limit here is 60mph, and the fastest flow of traffic will travel up to 70mph, and ultimately get pulled over.
Dedicated high-speed cruising on highways across the globe is what the twin cylinder 600/650cc GT scooters are for.
You should go for a 650.