Yamaha YFZ450R Top End Rebuild

Welcome to our YFZ450R top end rebuild project, our comprehensive video guide in which we show you how to tear down and reassemble a Yamaha ATV and get it running again.

A top end rebuild on a Yamaha ATV is a major undertaking. In the video above, Partzilla's own John Talley takes you through the whole process step-by-step, including engine disassembly, the top end rebuild, and how to put it all back together again. 

PRO TIP: Use our Yamaha YFZ450R exploded parts diagrams for additional reference.

Watch the videos below to see this Yamaha ATV engine rebuild broken up into three separate sections: Teardown, Top End Rebuild, and Reassembly. 

Part 1 – YFZ450 Top End Engine Teardown

In part one, John shows you how to take apart the YFZ450 engine to prepare it for the top end rebuild.

When disassembling the YFZ450R, the plastics have to come off first. Next, the gas tank and the exhaust have to be removed on the Yamaha ATV. Once those parts are off, the engine teardown begins. John shows you how to remove the valve cover and find top dead center. Next comes the removal of the cam chain, the cams, the head and the piston. 

Part 2 – YFZ450 Top End Rebuild

In part two of this series, John shows you how to perform the entire YFZ450 top end rebuild with the engine disassembled.

Taking apart the YFZ450’s top end is one thing, but rebuilding it takes a little more skill and the right parts. In this section, John shows you how to correctly position new rings on the piston. Next, John walks you through how to connect the piston and set the table for installing a new cylinder. After that, see how to get the head in place and the timing chain on and set the timing. Finally, see how to get some fire into the Yamaha ATV motor by replacing the spark plug. 

Part 3 – YFZ450 Engine Reassembly & Installation

With the top end reassembled, there are a few more things to take care of before breaking it in. In part three of this series, the top end rebuild is complete, the engine is as good as new, and John shows you how to put it back together and reinstall it. 

See how to install the airbox onto the YFZ450, and then get the exhaust back on. An ATV won’t run without gas, so the next step is getting the fuel tank bolted on and connected. Finally, John cranks it up to make sure it’s working and then gets the plastics back on.