Moped de-restriction information

Disclaimer: We do not recommend or endorse the de restriction of mopeds. You follow any instructions here at your own risk.

If a Moped is de-restricted.

It becomes a 50cc Motorcycle. DVLA should be informed and the vehicle re-registered.
It may not conform to motorcycle requirements and may not be legal. For example; Lighting requirements are different for Mopeds and Motorcycles.
A motorcycle licence will be required. A 50cc motorcycle has the same licence requirement as a 125cc.A Motorcycle can not be ridden on a provisional motorcycle licence before basic training is completed (CBT).A full car licence may allow a moped to be ridden but not a 50cc motorcycle.
A rider must be at least 17 years old. A 16 year old can ride a Moped but not a 50cc Motorcycle.
The Insurance company who are insuring the vehicle should be informed. The premium will probably be un-affected but any modification should be notified to the insurer in writing. Insurance may be invalid if the vehicle is modified and the insurer not informed.

Restriction of 50cc 2 stroke twist and go engines.

Non catalysed engines.

All engines will have:

A spacer between the front pulley halves. (stops it obtaining the highest top gear ratio)
A branch pipe on the exhaust. (stops the engine revving beyond a certain point)

In addition, water cooled engines will have:

Older engines, starting with the first Runner and NRG MC2. Have a tube spot welded into the inlet end of the silencer.
Newer engines, have a tube seam welded into the out let end of the exhaust pipe.

All these restrictions can be removed without the need to re jet the carburetor.

Catalysed engines.

Have the spacer and the branch pipe. These engines will need a larger main jet, four sizes up on standard.
Do not remove the brass baffle plate from the carburetor bell mouth if one is fitted.
It is worth blanking off the “secondary air pipe” going to the exhaust just to ensure reliability.

In addition, it is worth fitting lighter rollers and blanking off the secondary air system. The roller weight has no affect on top speed but initial acceleration will not be very good with the heavier rollers because it will get into high gear too quickly. Original rollers on most current 50's are 6.4 gr. CM1102025. Replace these with 5.3 gr (orange) rollers CM1102035.

The secondary air system has nothing to do with performance but the reed valve may fail on
the higher power engine because the pulses it is subjected too are much greater, blank it off to improve long term reliability.

Restriction of 50cc 4 stroke twist and go engines.

All engines:

A spacer between the front pulley halves.
An electrical restriction in the CDI unit. Make a 3mm deep cut with a hacksaw in the position shown. You are cutting through a wire which you will be able to see in the slot. Make sure you have gone deep enough to completely cut through it. Then fill the slot with silicon. If you have a Kokusan CDI then you make the cut about 42 mm from the end.
They will need a larger main jet. Click here for the jet.

The restriction is the same on all 50cc four stroke models including the LX 50 4t, Fly 50 4t and Zip 50 4t (China). The main restriction on the 50 cc four stroke engine is electronic. There is no restriction in the exhaust pipe.