Very preliminary cost analysis for trip, if I am missing something let me know:

1,400 miles, average 40mpg = 35 gallons @ $3.75/gallon = $131

3 nights of hotel rooms (camping may be an option) @ $40/person = $120

Wear & tear on motorcycles (tires, oil changes, etc.) – rough estimate = $250

Food @ $5/breakfast, $10/lunch, $20/dinner per day for 4 days = $140

Gear will vary depending on what you currently own.

To use your own motorcycle will cost approx. $643 for the whole trip.

To rent a bike (approx $375) = $768 total trip cost