I disagree, Mmach 5 - the simple forward momentum of the bike doesn't keep it upright, it just keeps it moving forward. If you slid an upright piece of plywood on it's edge along a skating rink and let go, the forward momentum wouldn't stop it from falling over to the side. The only kind of momentum that might keep a bike upright is the "angular momentum" of the spinning wheels, which we in this thread have nicknamed "gyro", short for gyroscopic effect. My experiment was an amateurish attempt to see how effective that force is, since I no longer have the skill or knowledge I might once have had, to actually do the physics calculations.
Robert