Replacing Crankcase

I have to replace the crankcase on my YZ450F. I mechanically minded enough, if I take my time, to do most things with my bike. However, this seems like a tremendous amount of work. On a scale of 1 to 10 what would be the difficulty level of this task? Should I just bite the bullet and get the local shop to replace the cases for me? Any opinions welcomed.

Thanking you in advance,

Beyond rebuilding the shock and forks, there is not anything more tedious then splitting the cases. You should have the special tools to split and install the cases so you dont do damage to anything. If you dont have the tools, tear the motor down and out of the bike and just have the shop split, fix and seal the cases back together for you.

I second that! I was going to replace my cases when I got a whole in the top from a connecting rod that decided to split until about 4 hours into the job....I started looking at all the little pieces and how much work was still left....found it easier to just buy another used motor and swap motors entirely. Now, she runs like a raped ape!

I blew a chain through the cases when my 450 was fairly new. I had never had a 4-stroke apart before and was naturally worried. No problems. My only hitch was in not reading the manual about resetting the chain tensioner. My bike has worked flawlessly for the past two years since the rebuild.

I even cut the old bearings out of the old cases to save money. I couldn't remove them any other way.

Go for it. You can always take your engine to the shop in a basket. :thumbsup:


Anyone ever JB Weld something like this? Do you think that this may be an option?


I split the case on my 2002 YZ250F, it was a bunch of work but if you follow the manual closely it will go fairly smooth. The only special tools I needed were: impact wrench, flywheel puller, bearing puller and a torgue wrench. I actually enjoyed the project but it was the middle of the winter so I was in no hurry.

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