Originally Posted by ken cummings
See if there is a couple of inches between the seat tube and the rear wheel. Those longer chainstays are a mark of a touring grade bike. Does it have fittings for racks and 3 water bottles? Does it have a long arm rear derailleur for a wide gear range? Clean it up and get it running in any case.
Measure the chainstays from the bottom bracket to the rear axle. For a good touring bike it should be in the range of 17.5" or longer. Shorter than that and you start to have handling and fit issues when loaded. (Personally 17.5" is too short for me.) Also look to see how it compares to a Trek 520, Cannondale T800 or Fuji Touring. Although there are other touring bikes out there, these three are more readily available for comparison.
Don't get wedded to the old bike however. Lots of people get real nostalgic about old bikes - I know I used to be one of them- but a nice modern touring bike may cost you less and work much better than some old dog you have hanging around, especially if it's a nothing special Motobecane. That bike may be a good place to get you feet wet, if you can refurb it for very little money, but if you find yourself spending more than $500 to get it up to speed, cut your losses and look for a new bike.