Model Specifications

The PX125 dates back to 1978 and has had various modifications and improvements since then. The major changes are:

1982/83 models use a derivative of the P200 gearbox with lower primary drives, and have electronic ignition and autolube as standard (in the UK).

1985/86 EFL models introduced the latest gearbox. Ratios are the same as T5 but they still use a 6-spring clutch.

The PX150 was only available in the UK (officially) until 1982, when the learner laws changed from 250 to 125cc.

In 1999 models a disc was introduced.

Most performance improvements to these machines are based on improving power output and raising the gearing to make best use of the improved power. Modifications to obtain the best reliability are desirable and mostly obtained by using components from the latest machines.

Cylinder

The standard cylinder bore is 52.5 for the 125 and 57.8 for the 150. Capacity increases can be made by fitting a PX150 cylinder and head (125 only!), a big bore standard style VE cylinder at 61mm (166cc), a Malossi 61mm (166cc) kit, Polini 63.0mm (177cc) kit or one of the cheaper DR/Olympia 63.0mm (177cc) kits.

All the above are cast-iron cylinders. The only aluminium Nicosil cylinder is from Pinasco at 63mm (177cc), but this does not produce the power of the Malossi or Polini cylinders, especially when the crankcase inlet modifications recommended by the manufacturer are carried out.

Our personal preference is to use a Malossi or Polini cylinder. The Malossi, despite its smaller capacity, has a better porting layout and cylinder head and gives better power when inlet modifications and larger carbs are used.

The cheaper DR/Olympia type 177 cylinders are useful when a large increase in punch is required but not necessarily a large increase in top speed. They are not that far behind in performance if they are just bolted on, but the more work that is carried out to the motor the greater becomes the advantage of using a Malossi or Polini cylinder.