Polini injects adrenaline into these Yamaha engines and reinvents a classic

When this Italian company decides to reinvent a classic like the Minarelli vertical engine, it does so without concessions.

This is how the new Polini 70 Evolution thermal group is born, a high-performance kit that not only improves figures. It also  transforms the personality of the Yamaha Minarelli engine.

With a displacement of 4.27 cu in. (70 cc) and a construction entirely in cast iron, the new cylinder has been redesigned from the ground up. No hybrid experiments.

This is how it manages to mark a turning point. This is not a simple increase in performance. We are looking at a thorough, technical, and functional revision of the concept of preparation in compact engines.

Polini is a specialist in scooter engines

The key is in the details, and Polini has worked on them with care. The cylinder incorporates an  oversized reed valve box directly integrated.

It features two additional ducts that feed the side transfers directly. This system, unprecedented in engines of this architecture, allows for increased torque from very low revolutions. In addition, it provides an immediate and forceful response.

To accompany this solution, the kit includes a four-petal reed valve box, instead of the usual two. It adds a specific flow guide that reduces losses and channels the air and mixture with greater precision from the manifold.

This, by the way, is 360° rotatable, compatible with Polini CP carburetors from 0.67 to 0.94 in. (17 to 24 mm). It accepts both original and high-flow filters. Everything is designed to facilitate the finest adjustment, without sacrificing functionality during assembly.

The piston, with double ring, works together with a  competition cylinder head with copper gasket. Likewise, the kit includes 0.008 and 0.012 in. (0.2 and 0.3 mm) spacers. This way, the squish is optimized according to use and the rest of the mechanical assembly.

Polini offers two versions:

1. Code 166.0074/E, with 0.39 in. (10 mm) pin
2. Code 166.0074/12E, with 0.47 in. (12 mm) pin

Both allow, in a basic configuration, to reach 14 real hp with a wide torque curve, clean and full from low revs.

There is a key difference compared to other cast kits in its category. This Evolution stands out for its flexibility and for performance that doesn't require always being in the high rpm range.

To get the most out of its potential, the manufacturer recommends combining it with a CP carburetor between 0.75 and 0.94 in. (19 and 24 mm). Also with a Polini For Race or Scooter Team exhaust, and a High-Speed transmission.

It is available for €244.00 + VAT. It is defined as a true statement of intent for those who understand that, in 2T mechanics, true evolution is in the details.

Without forgetting that, like every Polini product, it is 100% made in Italy.