As we all know, you can get more with a gun and a smile than you can with a smile alone. If you're thinking of raising a few bucks by jacking a vehicle at gunpoint, your best bet is to pick a candidate out at the local supermarket, wait until the owner has loaded the groceries, and then accost him or her with the gun, take the keys, and leave with the vehicle and the groceries.
The wrong way to do this is to walk up to a group of bikers, pull your gun and demand the keys to the bike that appeals to you the most. Keep in mind that just getting started requires both hands and both feet which means you have to quit waving the gun about well before you make your getaway.
Bikers are notoriously possessive of their rides and even in New York where "everyone" is disarmed, this sort of effort is unlikely to end well for the thief. In this case, to quote Boris Badenov, "I love story with happy ending!"