Italian Motorcycles

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Aprilia ST125 1982 Strada

The 125 Strada was the first 125 road motorcycle produced by Aprilia. Presented at the Milan Motor Show in November 1981, the ST125 became available in October 1982 after extensive testing.

The ST125 was offered in three colour schemes: pearl white, pearl red, and metallic grey and black.

Powered by a Hiro engine derived from their motorcross models, the ST has conventional lines and was initially presented without a bikini fairing. Production models had an abreviated fairing as an optional extra.

The ST competed with machines like the recently released HRD and the Malanca in terms of performance and sporting appearance for the attention of the 16 year-old target audience. It won, as it much more reliable and also better finished.

The ST was also up against such sophisticated machines as the Laverda LZ 125 and the Zundapp KS 125 WK, both of which were liquid-cooled and very well presented.

The ST 125 remained in production in 1984 alongside the newly released STX. The '84 version retained its previous appearance and chassis, whilst the STX sports an Aprilia engine, readily recognised by the marque's name on the crankcase covers. During 1984 the STX received a new exhaust system which replace the long black chamber.

The front end of the ST has a large rectangular headlight and substantial instrumentation.


The ST frame was a conventional tubular closed double cradle equipped with Marzocchi 32 mm forks. Rear suspension was far from conventional - Sebac progressive monoshock suspension named APS (Aprilia Progressive System) made its first appearance. The APS was derived from the firm's off-road machines and was well-tried.

Grimeca supplied the 240 mm front disc and twin-piston caliper, along with a 160 mm drum at the rear. The wheels are both 18″.


Supplied by Hiro Motori of Origgio who had worked with Aprilia since the mid-1970s, the engine is a version of the highly succesful unit produced for their off-road models, extensively revised for road use.

The engine has some interesting features, among them:

Induction is by H.I.S. (Hiro Induction System) which has both piston-port and reed valve.
Forced circulation cooling activated by a pump and extended to the crankcase, i.e. a more efficient system than the thermosiphon circulation used in the Laverda and Zundapp cooling systems.
Dell'Orto PHBH 28 A carburettor
Six-speed gearbox.

The Hiro delivers 18.07 hp at 8250 rpm giving a maximum speed of 126.8 km/h.

Adapted from an article at autoemotodelpassato

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