Cracked Case by clutch arm

Last weekend I had an issue I would like to know if anyone else has had and what could possibly be the root casue:

While riding single track I heard a strange noise coming out of my motor (06 yz 450). It sounded like something may have come loose or broken off inside my lower end and was rubbing on rotating parts. It went away as quickly as it came on. I shifted my bike down to first and back to third where I had been riding, used my clutch, and used the brakes as well. Everything seemed fine. I suspect one of my gears may have sheared of a chunck of metal but wasn't really sure. The reason I say this is when the noise occured the bike jumped out of gear. I stopped to take a look and nothing looked out of place.

I rode it our about 1 mile to know where I could come back with the truck to get it and it ran just fine. When I stopped to look it over, one of my buddies noticed it was spewing oil right out of the engine case, right where the clutch arm is located on the left side. After wiping it off we noticed cracks in the engine case and a fair amount of oil on the frame.

I have not started it since and took it out of the woods with my truck. Any ideas what this could be? This bike has been well maintained but I do have at least 300 hours on it and have done one conplete top end at 150 hours. No real indication this was coming but it does seem to have been shifting a little notchier than usual in the last few rides.

At this point I want to fix it but realize the bike isn't worth much but a new one is cost prohibitive right now. Whatever fi I do, I want to be as permanent as possible.

If anyone has any suggestions I would appreciate a response. Any idea how much or availability on a new motor? I think I might be looking at major lower end work, a fresh top end, and some tig welding on the cases...if so, I need to evaluate other options as well.


Did you ever do the shift indexing lever mod? (replace the bearing for the bushing?)

No I haven't. I have not done anything with lower end.

And what is weird is the last mile or so I ran it out of the woods everything worked fine and sounded fine, but I was left with cracks in my engine case...

Does anyone know if new 06-9 engines are even available? Has anyone ever bought a motor off of craigslist or ebay?


I've seen some complete engines on ebay, but they are usually $1200-$1900 and used, which seems pretty pricey to me for a used engine.

Edited by Jim813

You need to replace the case on that side for sure sounds like a bearing failure (rare) or maybe a gear tooth broke and bound up and tried to push the shafts apart cracking the case. To do the job by the book it's likely at least a 1200 job. If you buy all new parts $1300 for a used engine will seem like a deal. If you know what your doing, and find good used parts you can cut the cost accordingly.

Thanks for the input. I figure about $2000 minimum since I would do a top end rebuild at the same time. I also agree a broken piece of a gear sounds like the problem. For that kind of money I want to get a few more good seasons out of it.

061900 I have parts shoot me a pm. I have everything you need....

All parts under 20 hours of run time.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now