BIG EVOLUTION CRANKCASE for HORIZONTAL YAMAHA MINARELLI ENGINES
The Big Evolution crankcase for Horizontal Yamaha Minarelli engines presents two main features. The most important one concerns the primary gear with variator driven pulley.
Polini Motori has projected a further working on the case so that it is possible to fit the supplementary gear that works on a pin to be screwed on the shaft itself. Thanks to this, the pin is less flexible while usually it is completely overhanging (photo 1).
Second important feature is the creation of air intakes on all the surface to improve the variator cooling.