Yamaha YZ450F Crankcase Cover Replacement 

When supercross competitor Scott Champion crashed his 2018 Yamaha YZ450F, he brought it to us to get some repairs done, including replacing the crankcase cover. 

The crash Scott discussed with our Yamaha motorcycle pro John Talley included, among other things, putting a hole in the crankcase cover. Watch the video above or follow the steps below to learn how to replace the crankcase cover on a Yamaha YZ450 dirt bike.

Yamaha YZ450 dirt bike crankcase cover

Tools and Parts - Yamaha YZ450F Crankcase Cover Replacement

  • 8mm, 10mm sockets
  • T25 Torx wrench
  • 10mm wrench
  • 4mm, 5mm, 6mm, 14mm Allens
  • Ratchet and extensions
  • Needlenose pliers

Buy Yamaha motorcycle crankcase cover

Buy Yamaha dirt bike crankcase cover gasket

Yamaha YZ450 Crankcase Cover Change

Step 1. Place a drain pan under the motorcycle, then remove the oil drain bolt from the bottom of the bike and let the engine oil drain out.

Yamaha YZ450 oil drain bolt

Yamaha YZ450F oil drain

NOTE: The oil in Scott’s dirt bike was new, but it still needed to be drained out. However, there was no need for an oil filter change on this bike.

Step 2. Disconnect the motorcycle battery.

Yamaha YZ450F battery

Step 3. Remove the crankcase cover bolts, the cover itself and the gasket behind it. 

Yamaha YZ450 crankcase cover bolt

NOTE: One bolt at the very top of the cover has a copper washer behind it, so make sure you don’t lose it.

Yamaha dirt bike crankcase cover

Step 4. Pull the stator and the pickup coil out of the crankcase.

Yamaha YZ450 dirt bike stator

Step 5. Mount the stator onto the new crankcase cover.

Yamaha YZ450F crankcase cover stator

Step 6. Add red threadlocker to the bolts that hold the stator and the pickup coil in their place.

Yamaha YZ450 stator bolts

Step 7. Install the three bolts that hold the stator in place and tighten them down. 

Yamaha YZ450F crankcase cover stator mounting

Step 8. Mount the pickup coil into the crankcase, then install the bolts that hold it in place and get them snugged down.

Yamaha YZ450F crankcase cover pickup coil mounting

Yamaha YZ450F crankcase cover pickup coil stator

Step 9. Add a little bit of Yamabond adhesive around the groove of the crankcase to ensure it makes a good seal. 

Yamaha YZ450F crankcase cover seal

Step 10. Install the small plate that holds the wires back and tighten it down.

Yamaha dirt bike crankcase cover replacement

Step 11. Mount the new crankcase cover gasket onto the machine, followed by the cover itself.

Yamaha dirt bike crankcase cover installation

NOTE: Be careful when pressing the crankcase cover on, since the rotor has magnets in it and it's going to try to pull in. Don't let it pinch your fingers when you go to seat it.

Yamaha YZ450F crankcase cover installation

Step 12. Reinstall the crankcase cover bolts, then get them snugged down.  

Yamaha YZ450F crankcase cover bolts installation

NOTE: Remember to install the copper washer along with the top cover bolt, which goes where the arrow is up top. Also, makes sure the two bolts at the bottom have the cable holders reattached before installing them. 

Yamaha YZ450F crankcase cover bolts installation

Step 13. Reinstall the inspection covers back onto the crankcase cover.

Yamaha YZ450F crankcase cover change

Step 14. Reinstall the oil drain bolt with its crush washer.

Yamaha YZ450F oil change

Step 15. Refill the engine with oil (half a liter for this bike), then check the site gauge to make sure the oil level is correct. Top off the oil if necessary and and you’re done.

Yamaha YZ450F oil change refill