How much horse power power does Althena big bore kit make yfz450r?

The Athena big bore kit for the Yamaha YFZ450R typically increases the engine displacement to around 462cc, which can result in a horsepower increase. While exact figures can vary depending on additional modifications and tuning, users often report horsepower gains of around 5 to 10 horsepower over the stock engine, bringing total output to approximately 50-55 horsepower. Proper tuning and a good exhaust system can further enhance performance.