Originally Posted by motogeek

It's odd for a GB stem to be on a Motobecane. Usually they were on Raleighs and other British bikes. Motos normally came with Pivo or Philiipe stems and bars. The diameter on GBs and the French stems are not the same, and the GB may have been forced into the Moto steerer tube, sometimes creating a split on the flat part of the steerer.