HOW TO MAKE YOUR DANGEROUSLY SLOW 30MPH HONDA MT50 FASTER,  (forget about derestriction and all that, UK MT50's are not really restricted like the modern 50cc scooters they are restricted by the small 13mm Carburetor, the Reed valve stopper plate,crap cylinder timing,very restrictive exhaust, FIRSTLY START WITH A BIG BORE KIT AS THEY USUALLY RUN VERY WELL WHEN DONE PROPERLY, AND SEE HOW THE ENGINE ACCEPTS IT (if engine is in good working order it should all go as planned but if its worn out you will probably be needing an engine rebuild with a new crank bearings and seals,maybe even a reconditioned/new crank)

BIG BORE KITS

A Cheap 70cc-bore kit will cost around 60-80 quid, which should include Piston, Cylinder/barrel, Piston Rings and circlips.
This will give you a top speed of about 50-55mph depending on what sprockets you use(45mph orso with standard sprockets) , and also how the carburetor is setup and jetted.
But don't forget the new parts will have to be ran in (ridden very slowly for at least the first 300 miles to bed the new parts in) in other words don't thrash the engine, keep at low revs(earlier gear changes), be patient, good things come to those who wait.

Although there are better quality kits which are 70cc a bit quicker and last longer but are a bit more pricey, in the range of about 90-120 quid

Unless you were planning on tuning everything on the original engine.
I.E

 Bigger Carburetor 16/18/20mm (as the standard UK Carb is only 13mm for restriction purposes).
 Sports Exhaust (to get the fumes out quicker as there is more petrol and air coming in from the Bigger Carb).
 Racing CDI (to cope with the higher RPM of the engine) and a sports reed valve.

The best speed/money difference would be obtained by buying a RECONDITIONED HONDA H100 ENGINE and having the Frame and Exhaust slightly modified to accept it which isn't too difficult for a good motorcycle mechanic who knows what there doing.

Also you can fit a 1980-1982 honda CR80 6 speed gearbox and 4 plate clutch into the MT50/MT5/MB50/MB5 engine or even a h100 engine.

This is the best way of making your bike into a little powerful wheelie machine that would completely obliterate most scooters on the road.

I and my associates at Fast-scoot will not be held responsible for any problems caused to your moped during self modifying,experiment at your own peril.