Well, lets think about this for a second....

1. Both 4th and 5th gears are overdrive gears (0.906:1 and 0.750:1), which takes a lot more power to turn than a standard underdrive or 1:1 gear. (NOTE: the above state gear ratio's don't take the transfer cases 35/32T reduction ratio of 1.09:1 into consideration)

2. The Roadie engine peaks around 3600rpm (give or take a couple hundred), so going higher really isn't going to gain you much unless you've swapped cams, pistons and had the heads warmed over.

Theoretically, in 5th gear with a stock 33T front pulley (1600), the bike should be capable of reaching a calculated top speed of 169.4mph @ 5,000rpm. However, that calculation doesn't take several variables into consideration (weight of bike, road resistance, wind resistance, weight of passengers/gear, etc.). All of those forces will greatly decrease the potential top speed, and the faster you go the greater their impact will be (percentage-wise).

Now, if we adjust the calculator's data to set 3800rpm as the max to correspond with our engine's powerband, we get a max top speed of 128.7mph @ 3800RPM in 5th gear. Factor in the 10-15% loss for the variables and you're down to 109 to 116mph.

You'd have to do some serious internal engine work to move the engine's powerband up into the higher rev's to get much more speed.