What's worse than breaking down?
Not having any way to fix it. Get prepared.
Every motorcycle tour website has its checklist for the "necessary" tools and repair items. Before you run out and buy 20 pounds of gimcracks and goo-gaws that will likely return home untouched, consider a few things:
Put it where?
How much room do you have on your bike?
I did my coast-to-coast on a 2012 Triumph Bonneville, which has, how shall I put it, zero cargo capability. This is a good way to start, because limited cargo space prevents you from saddling your bike with 30 pounds of unnecessary crap.
Cavernous hardcases practically beg you to fill them to the brim. Set yourself a limit that's at least twenty percent below your total capacity. You'll pack smarter and have space for stuff you buy along the way. I ended up getting a luggage rack and some waterproof luggage, along with a nice tank bag.
Remember also that when traveling across the US, the penalty for forgetting something is usually small. There are these things called "stores," where you can buy nearly anything you've forgotten.
From Each According to His Ability
If you don’t know how to repair anything more complicated than a clogged fuel filter, a huge tool roll is not going to help you. And even if you can rebuild the engine with your eyes closed, do you want to do this on the side of the road? On your vacation? Consider it all part of the adventure if you want to, but I’d rather take day-trips on a loaner or rental while a local mechanic works his magic.
Foggy Mountain Breakdown -- The Basics
Don’t forget to buy a towing/roadside repair membership with AAA or the AMA. This is a no-brainer. Read the fine print and make sure you’re getting some serious free towing distances. I have the AAA mega coverage, because my kids are tough on cars. I get far more than my money's worth every year.
And before you buy, check your insurance policy (you do have insurance, don't you?) to see what your coverage includes.
Even with roadside coverage, you'll want to fix simple things yourself. It’s also great to be able to help a stranded, less-prepared biker. Take these things:
Flat repair kit with CO2 cartridges
Pocket knife/small Swiss Army knife
Permatex black gasket sealant
Roll of Velcro
Chain brush and lube
Posi-lock connectors for electrical work. These are amazing. If you’re working in the dark on the side of the road, these are the ones you want.
Ratchet wrench with two or three sockets in sizes that will allow brake and electrical work as well as tank removal.
Needlenose pliers with wire strippers
Some hex keys. Check your bike to see which sizes you need.
Screwdrivers. Can be used to pry and jab as well as turn screws.
Gorilla Tape or similar
Long zip ties. LONG ones. You can cut 'em shorter, but you can’t make ‘em longer.
It doesn't have to be like this. The less you take, the happier you'll be. But you have to take the right stuff.
I don't carry a gun on long-distance motorcycle trips. Some little old lady in the Denny's parking lot is going to see me transfer it to my luggage and call the cops. I don't need the aggravation.
Strong, small flashlight
Extra headlight and taillight bulbs. I have never taken them and never needed them. But maybe you should. They're light and small.
Haynes Manual or similar. It doesn't take up much space and it might come in handy if you're the only mechanic available.
Prepping the Bike
There is no good reason to start a long motorcycle trip with any part of the bike near the end of its service life. Do your tires look iffy? Get new ones. Change the oil & filter, check the fuel filter, tire pressure, all that stuff. Check your electrical system. If applicable, check your coolant. Go around and make sure everything is tightened up.
Consider buying a power block, which makes it a lot easier to add electrical doodads like a USB charger, heated grips, or glove/vest ports.
The Tank Bag
I use my tank bag to carry food, water, maps, my phone and small things like pens, notebooks and toll change. Try to keep the tank bag neat and light, otherwise you've canceled out its purpose of having certain things close at hand.
I am an enthusiastic practitioner of my Second Amendment rights, but I have never carried a gun on any cross-country trip. First, the laws vary significantly from state to state. Keeping track of who allows what and under what circumstances is a pain in the ass. Second, a gun would be another thing to worry about being stolen or lost, certainly more so than a GPS or GoPro. Third, some little old lady in the Denny's parking lot is going to see me transfer a gun to my luggage and call the cops. I don't need the aggravation.
What did I miss? Add it in the comments.