Honda CRF450X Complete Engine Rebuild Video Guide | ProX

June 25, 2020 / by Kevin Bailey

We brought a well-used Honda CRF450X engine into the shop for a complete teardown and rebuild, top to bottom-end. We documented this engine rebuild every step of the way, explaining key tips and information you'll need to know during the critical steps curated into a 12-part video series covering countless four-stroke dirt bike engine rebuild pointers.

The Honda CRF450X is a staple in the four-stroke off-road dirt bike world. The bike was essentially exactly the same from 2005 all the way through 2018, and that's because it worked, and worked well. There is a huge number of these bikes and engines out there and we wanted to do our part to help our fellow riders keep as many of them on the trail as possible.


This rebuild began with a four-part video series covering all the teardown and disassembly tips you need to know.

ProX CRF450X Rebuild: Teardown Part 1, Top End

Part one of the CRF450X engine teardown covers key tips in regards to head and valvetrain disassembly, including removing the camshaft and cam (timing) chain.

ProX CRF450X Rebuild: Teardown Part 2,
Flywheel Removal

The second installment of the CRF450X rebuild covers the flywheel removal portion of the teardown. Proper tools and careful handling is crucial here to prevent damage to components you might be reusing.

ProX CRF450X Rebuild: Teardown Part 3,
Clutch and PTO Side

Moving to the clutch side to continue disassembly, we cover key tips on removing clutch components as well as the PTO gear, idler gear, and similar components.

ProX CRF450X Rebuild: Teardown Part 4,
Splitting the Cases

In the final episode of our CRF450X teardown, we finish up disassembly by splitting the cases and removing the remaining components, such as the crankshaft and transmission. Follow along and don't miss our key tips along the way!


Part 5 marks the beginning of reassembly of our CRF450X engine. All the engine components that will be reused have been inspected and cleaned and a list of new ProX parts that will be used throughout assembly have been gathered. We begin assembly with showing you how to install bottom end seals.

ProX CRF450X Rebuild Part 5:
Assembly, Bottom End Seals


Want to find engine parts for your rebuild? Search and find by application here!

ProX CRF450X Rebuild Part 6:
Transmission Assembly

Transmission assembly is an incredibly critical part of reassembly and can cause a lot of damage if done incorrectly. Watch along step-by-step to ensure your transmission operates smoothly.

ProX CRF450X Rebuild Part 7:
Crankshaft Installation and Case Assembly

With the case halves each prepped and transmission installed, we now drop in a brand new ProX complete crankshaft assembly and join the cases together.

Check out more on ProX complete crankshafts here!

ProX CRF450X Rebuild Part 8:
PTO Side Assembly

We go step-by-step through assembly of the various PTO side gears and components, including balancer and idler gears, shift star, one-way clutch, and more.

ProX CRF450X Rebuild Part 9:
Clutch and Flywheel Installation

Our Honda CRF450X engine rebuild continues with finishing up the PTO side assembly,
re-installing the clutch with a new ProX clutch pack kit, re-installing the flywheel, and equipping a new ProX cam chain.
Check out more clutch repair tips here and find ProX clutch parts for your machine here!

ProX CRF450X Rebuild Part 10:
Piston Prep and Installation

We've finally buttoned up the new bottom end of our CRF450X engine and it's time to move on to the top end! In this episode, we unbox a new ProX piston kit and cover each step in properly preparing and installing a new four-stroke piston.

Check out our complete 4-stroke top end rebuild guide here!

Need a piston for your bike? Find one for your application here.

ProX CRF450X Rebuild Part 11:
Valvetrain, Head Rebuild

We show you how to install new valves and springs, reassemble the remainder of the valvetrain, and check valve lash. A new ProX valve and spring kit, as well as a ProX shim kit helped us make sure this 450X valvetrain is ready to go!

Check out our complete guide to installing valves here, and our
guide to 4-stroke head rebuilds here!

Need valvetrain components for your machine? Find them for your application here.


ProX CRF450X Rebuild Part 12:
Final Assembly

In this final installment of our CRF450X rebuild, we finish top end assembly and button up the last few items to complete this engine. With ProX components from the bottom to top end, this Honda CRF450X engine is now back to showroom floor performance without breaking the bank!

Whatever you may be rebuilding, ProX takes pride in offering performance replacement parts that deliver OEM or better quality while keeping it easy on the wallet!
Search parts for your machine here.

Topics: featured, Powersports, ENGINE TECH, Tech, Maintenance, How-To

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