2004 Yamaha
YFZ450
MSRP $0
From the bottom up, the YFZ's dry-sump motor is a WR/YZ hybrid re-engineered specifically for the demands of quad life. To make the YFZ legal for the ATVA's Pro-class series that has a displacement limit of 440cc, the Yamaquad's stroke was decreased by 1.4mm, making it a "439" rather than a true 450.