Its for a few reasons. The ones that I can member the now are 1, Lighter set up. 2, Weight is more centered on the bike. 3, Smaller cogs so a better roll over hight.
Which makes it all the more fun when your up on the hill and the clutch goes. You really need to learn how to match the engin speed to ground speed pretty fast there.
The pilot was ice skating on the loch on thursday. Thats about 100 feet deep. Not that stupid. Just strange seeing a helicoter below you sliding about the place.