Really confused now. If you apply a 4.9V input without a voltage divider to an adjustable regulator, I'd expect the output to be 4.45V as the regulator tries to (without success) increase the output voltage to maintain VREF at 1.25V. But the same would occur for a 5V fixed regulator -- you'd just be seeing the dropout voltage.
What do the part markings on the body of the LM1117 say?
The Rugged Motor Driver
: two H-bridges, more power than an L298, fully protected