Adding motorcycles to your list of possible bug out vehicles gives you a lot more options for your potential bug out scenario. Ideally, a bug out vehicle is one that can take you off road and carry you and your bug out supplies without difficulty. When considering a motorcycle as an option, it's important to note the advantages and disadvantages.

Advantages
1.) Fuel economy. You can travel much further on less fuel, and this could mean the difference between surviving and not in some cases.
2.) Easy to store and hide at a base camp, at home or anywhere you end up. Once out of the disaster area you can conceal/camouflage a motorbike rather easily as compared to a full sized motor vehicle.
3.) Avoid gridlocked highways, and road barriers/obstacles, but you have to be careful and know your bike’s off-road capabilities before setting off cross-country as you try to avoid traffic jams.
4.) Leaving quietly is another advantage. You can push the bike far enough away so when you do start it and it happens to alert anyone you have a good head start.

Disadvantages
1.) Limited cargo space, even though the fuel economy compared to a motor vehicle is considerably better, you would still need fuel at some point. Unless you have a cargo trailer attached you would not have the ability to carry fuel with you.
If you do have a cargo trailer, then you have pretty much limited yourself to relatively good roads and certain trails or pathways.
2.) No protection from the weather and this could be a major concern in some areas of the country. Limited to no cover at all from thrown objects, gunfire and other projectiles like arrows, bolts or even steel balls launched from a slingshot.
3.) Snow will slow or stop you completely, as would ice.

So, obviously, the biggest disadvantage to using a motorcycle is the lack of cargo-carrying capabilities. Although you can hitch a small trailer to a motorcycle, this drastically limits the maneuverability, and if this is your plan you may just want to have a 4×4.

However, if your only concern is to transport yourself to a bug out location and you need to carry minimal supplies, a motorcycle may be the ideal vehicle for you. They get excellent gas mileage and can drive through backed-up highways and off-road with far more ease than a traditional vehicle.

All-in-all, there's a lot to consider. But if your needs align with the abilities of a motorcycle or dirt bike, you may just want to consider it as an option.

For more on this topic visit Preparing for SHTF.