Ducati 500GP V-Twin Desmo Racer | A very rare bike!

Phil Aynsley celebrates his 100th column showcasing the rare Ducati 500GP

March 29, 2018

Ducati Desmodromic 500GP

With Phil Aynsley

This is possibly the most original of the five Ducati 500GPs built

Well who’d a thought it! My 100th column. To mark this unlikely event here is a bike of not only major historical significance but a Ducati as well!

The 500GPs are, as you'd expect, quite hard to track down — The 500GPs are, as you’d expect, quite hard to track down

Over the years one Ducati I was most keen to photograph was the rarest V-twin – the 500GP. However they aren’t the easiest bike to track down (apart from the one in the Ducati Museum), so it took me until a visit to Germany in 2016 to finally get one in front of my lens.

The 500GP was built as a proof of concept for the brand’s 750cc roadbike and included Desmodromic valves

The 500GP twin was developed from late 1970 and was intended as a ‘proof of concept’, in order to help the sales of the 750cc road bike that was just entering production. While the motors shared the same basic L-twin layout, the 500s used a much squarer bore/stroke ratio and was equipped with Desmodromic valves from the outset.

After the first race the standard frame was replaced by a Colin Seeley commissioned frame

Its first race was at Modena in March 1971, and while the original factory chassis was initially used, it was replaced from August onwards by a Colin Seeley commissioned frame. The front drum brake was also changed to a disc before proper racing was begun.

Riders in the first year of competition were Bruno Spaggiari, Phil Read, Ermanno Giuliano and Gilberto Parlotti

Riders during this first year were Bruno Spaggiari, Phil Read, Ermanno Giuliano and Gilberto Parlotti. It was Parlotti who gave the 500GP its only victory – at a non-championship race in Yugoslavia in May.

The front drum brakes were also replaced for rotors for racing — The front drum brake were also replaced for rotors for racing

Read scored a second behind Agostini at San Remo with other 500GPs in third and fourth places. He also finished fourth at Monza. Spaggiari and Paul Smart finished third and fourth respectively at Imola the following year.

The 500GP was also given a lower priority than the 750 at the time, development wise

The 500 project took a lower priority to the successful Formula 750 bikes so were never developed to their full potential. Engineer Taglioni did experiment with the design however.

A four-valve head was also tried in 1972, but wasn't quite producing the same power as the two-valve — A four-valve head was also tried in 1972, but wasn’t quite producing the same power as the two-valve

A four-valve head was tried in ‘72, but it made 69hp compared to the two-valve heads which had reached 71hp by that stage. Fuel injection was also experimented with the same year but this went nowhere as the FIM banned its use.

In 1973 Renato Armaroli further developed the machine into a belt-driven DOHC eight-valve

In 1973 Taglioni employed noted engineer Renato Armaroli to develop the 500 further. A belt-driven DOHC, eight-valve was the result. It was raced several times during the year by Spaggiari but without success. Its output of 74hp was not much of an advance on the two-valve motor.

The Amaroli 500GP — The Ducati Prototipo

Of the five 500GPs built this one is probably in the most original condition.

In a strange coincidence, a few days later the owner of the next collection I visited in Germany was showing me his bikes and what should I spy but another 500GP!