How big can you make a yz450f?

The Yamaha YZ450F is designed primarily for Motocross and off-road performance, with a displacement of 450cc. While you can make modifications to increase horsepower and torque, such as adding a high-performance exhaust or tuning the ECU, there are limits to how much performance you can realistically extract without compromising reliability. Additionally, any modifications should comply with local regulations and safety standards. Overall, the bike's design inherently caps its maximum potential size and performance.