To determine the reaction on the front wheel, we do a momentum balance on the rear wheel aligned with the center of mass:
W(1) = W(0.5)(1) + R(0.5)
R = W
For the motorcycle to accelerate, there must imbalance of forces, so:
ma = R - F
since friction is not limiting:
ma = mg(1 - 0.5)
a = 0.5 g
Therefore, the acceleration is 0.5 g or 0.5(9.81) = 4.91 m/s2