The Rok Junior aligns itself to the Senior by adopting the same Vortex 125 GP engine, but with a throttled exhaust. On the Viterbo track we verified how one can easily pass from one to the other configuration without problems.

TEXTS: MAURIZIO VOLTINI –

PHOTO: DOMENICO PAOLICELLI WITH THE COLLABORATION OF OFFICINE IN PROGRESS

The new competitive racing season of 2019 will see a fairly decisive change in the Rok Cup, namely in the Junior class in the championships taking place in Italy and in several other countries. In fact, the cadet category will be aligned to the Senior as regards the engine used, going from former Vortex 125 Rok “classic” to the latest GP model. Similarly to what was already happening, to differentiate the two categories there will be the addition of a “restricted” exhaust manifold on the Junior: a 25 mm diameter section (versus the Senior’s 38 mm) which reduces the power by 22 hp and, consequently, also the lap performances, which otherwise could have increased due to the different minimum weight between the two categories. In fact, we are talking about 145 kg for the Junior versus 160 kg for the Senior.

16 YEARS OF SERVICE

This modiication will deinitively say farewell to the adoption of the “classic” Vortex Rok, the engine that has given birth to this successful single-engine category since 2003. Marking the entry of Vortex in the sector of brand trophies and of Tag engines (ie with electric starter and centrifugal clutch), this 125 cc single cylinder reed engine featuring a Dell’Orto carburetor has created one of the most popular series in the world, with more than 400 drivers participating in the final. An engine that was gradually lanked first by the “throttled” junior variant and therefore also by its “little brother” for the 60 class, as well as by the GP and DVS variants, in addition to the Shifter model with gears. The Rok GP engine was initially adopted by the Super Rok category, destined for the most demanding drivers, thanks also to the higher power determined, among other things, by a bigger carburetor. Later, with the adoption of the usual 30 mm Dell’Orto, it moved to the Senior Rok category, while Super adopted the DVS direct drive. For a while, in order to soften the passage and to affect as little as possible – esp from the economic point of view – the choice to continue with the classic Vortex Rok was made in the Junior Rok, imposing the GP only in those countries just starting out in the cadet category and therefore it would have made no difference. But now even in those countries where the old Rok was still used, the move to the GP will be made, thus standardizing the series. This also provides a little more speed, given the greater performance of the Rok GP compared to the classic, for the different configuration of the cylinder, and for the presence of the pneumatic valve on the exhaust.