16 to ride a moped (50cc max speed 28mph), 17 to ride a 125cc (11Kw), 19 to ride an A2 motorcycle (35Kw) and 24 to ride an unrestricted category A motorcycle (unless you have held an A2 licence for 2 years)
You must pass both the Theory and Practical tests to ride anything other than category AM (moped) or A1 (125cc, 11Kw), unless supervised by a qualified instructor