Polini’s got some great stuff, and one of the latest additions to its catalog of parts includes upgrades for the Yamaha Minarelli engine.
With the goal of making more power and improving the resistances of the engine’s internals, Polini’s parts are specifically designed for the Yamaha motor, allowing the small engine to achieve bigger power figures. Two types of upgrades are available from the Italian brand, which include a range of crankshafts and new cylinder kits.
Starting off with the crankshafts, the Minarelli engines (found on the CY, MY, and CW models from the Japanese brand) will get better durability and resistance with this kit should the power be more than the stock parts can handle. The connecting rod is machined and can be used with a 12mm piston, an alternative to the 10mm on the original piston pin. This upgrade pairs perfectly with the cylinder kit, which allows for 40 or 70cc cast-iron cylinder kits. There are two part numbers available for the Minarelli engine whether in its horizontal or vertical configuration.
Polini For Race Ø 12 Crankshafts for Yamaha Minarelli
- 210.0048/12 - Yamaha Horizontal
- 210.0049/12 - Yamaha Vertical
The next upgrades are a selection of cylinder kits which includes the head, piston, piston rings, pin, and gaskets. Designed to work in tandem with the crankshaft, the 12mm kits are best paired and done together for compatibility and maximum power gains over the stock setup. The Polini cylinder kits feature an improvement in reliability over long periods of stress, and the special alloys used in the creation of this cylinder upgrade also offer resistance to high temperatures.
Cast iron is a very hardy material, and Polini is putting it on the head of the engine for durability. The head is otherwise paired with a special alloy on the skirt with high siliceous content for temperature resistance and performance. The piston rings that are included in the kit are made from a spheroidal cast iron, which is resistant to wear, rebored, and lapped according to the brand’s product page.
As for the piston itself, it’s made of a special aluminum alloy with a high coefficient of heat exchange. The combustion chamber has also been reworked for use with high compression ratios and it is also designed with high turbulence.
It’s important to note that this cylinder kit cannot be used without the crankshaft kit, so be sure to order them both at the same time as they’re supposed to be mated together.
Polini cylinder kits for Yamaha Minarelli engines Ø 12:
Both of the kits are made in Italy, and the prices aren’t as bad as you think. The crankshaft kit will set you back 139 EUR plus VAT, while the cylinder kit will cost you 150 EUR plus VAT. In U.S. Dollars, you’re looking at about $150 USD for the crankshaft and about $160 USD for the cylinder head kit not counting VAT.