ATHENA Big Bore Kit 300cc Yamaha YZ250F

The standard Yamaha engine is considered one of the best in the first part of power delivery: the initial thrust is exceptionally powerful, even though it is within the medium and high steady states, and strong initial progression seems to stabilize a lot.

Athena's Big Bore Extreme increases the displacement up to 304 cc, bringing the bike to have a very strong, effective and consistent engine output over the entire arc of the power delivery curve.