Suzuki Street Magic Mini-Bike TR50S
The UK spec version of this machine is not a full power engine fitted with restricters but an engine unit designed to comply with the current legislation. In comparison to the full power version the UK model has different cylinder porting (can be modified or replaced by 70cc kit), different exhaust system (must be replaced), different CDI unit (must be replaced), different gearing (must be replaced for any worthwhile increase in top speed).
The cylinder, exhaust and CDI unit are all tuned to each other, so changes to one will affect the others.
The easiest way to derestrict is to either fit full power parts from Suzuki or aftermarket performance parts. In almost all cases the aftermarket parts are cheaper and give more power.
The full power unit modifications are designed to raise top speed to around 70km/h (45mph). By using aftermarket parts this can be improved on by 10mph or more with much better acceleration.

Graph shows uprated Street Magic compared with standard
(The large variations for the tuned machines are caused by RPM variations with the standard pulley arrangement. The power drop in the middle graph at 33mph is caused by the original CDI unit being unsuited to RPM above 8,000.)

CDI Unit
The standard CDI unit reduces its ignition timing so that the engine goes flat at around 8,000rpm. Any parts that create power above 8,000 are wasted because of this. Aftermarket CDI units that run to past 10,000rpm are available. These transform any modified engine unit. The Suzuki full power CDI is tuned to suit the Suzuki full power exhaust and 50cc barrel, not higher revving motors.