I'm done with this!

Crank bearing. Heres my thinking.......the crank bearing have a groove in the middle of them for lubrication. When A crank bearing slips or gets crushed or warped due to multiple reasons(Cranked Down to hard. Not worked in(Plastegauging) the bearings before then finaly seat).

When they get crushed no lube(oil) can get in there for Lubrcation, friction(heat) can discolour the crank. So do NOT think the blueing is something normal

So do NOT think the blueing is something normal

I will personally guaranty right now that every brand new YZ450 crank looks exactly like that. All of them.

And with all the talk regarding crank bearings, and grooves, and Plasti-Gauge, I wonder what kind of car you're talking about. The YZ450, as with most modern singles, has a roller bearing rod, and ball bearing mains. There is no practical way to crush the bearing.

Well the engine was removed again and completely torn down. Turns out the left side crank bearing was shot. Some balls had started to chip and grove. Anyone know if a complete engine bearing set is sold or do I have to buy each bearing individualy??? I have looked on rockymountain and they only sell crank bearings, thats all I found on ebay as well.

This Might of been already answered but. Its the skid plate almost 100% sure. Motocross action just did a readers question on that noise.

Iceee187. Not sure if you read the thread but judging by your post you did not. It was a bad crank bearing that caused the noise. I am sick and tired of this catch all skid plate excuse. Read the thread please and add usefull information.

Iceee187. Not sure if you read the thread but judging by your post you did not. It was a bad crank bearing that caused the noise. I am sick and tired of this catch all skid plate excuse. Read the thread please and add usefull information.

your bike only has 36hrs. This would be the fastest crankbearing failure I have ever heard of. I am not saying this to doubt you, and I hope this is the issue. You will know after installing it and starting the bike that this truely fixed the issue. Do not be surprised if there is still a lot of noise after this...then you will know that unless you use foam between the skid plate and the motor there will always be a lot of noise.

"your bike only has 36hrs. This would be the fastest crankbearing failure I have ever heard of. I am not saying this to doubt you, and I hope this is the issue. You will know after installing it and starting the bike that this truely fixed the issue. Do not be surprised if there is still a lot of noise after this...then you will know that unless you use foam between the skid plate and the motor there will always be a lot of noise."

Why would anyone still try to blame a skid plate for an unusual noise??? I have stated that I have the skid plate on since day one. The standard engine noise which in itself is loud and a little uneasing in the first few rides was overcome by a much louder (much the key word) noise. I have torn the engine completely down and found chunks of a crank bearing ball. The largest was almost an 1/10th the size of the ball itself. Funny thing is I found absolutly no chunks of skid plate in there when I split the case.

Nope, it had to be the skid plate. :thumbsup:

This is what happens when you don't read through a thread before you post. :lol:

Something tells me the original owner put the hour meter on AFTER putting a couple hundred hours on the bike...

Looks more like the previous owner put the air filter on wrong due to the sand caked to the top of the piston when I tore it down the first time. Who knows, you get what you pay for. Thought I was getting a good deal and ended up with a money pit. Just need some new engine bearings now and all will be well.

Anyone know of a engine bearing replacement kit or should I buy the OEM bearings individualy from thumpertalk store???

I personally suggest OEM bearings for a lot of reasons...so get them individually if that's what you must do.

I personally suggest OEM bearings for a lot of reasons...
The foremost of which no doubt boils down to quality.

There are no kits that I know of, in any case.

All Balls makes a crank bearing kit, Rocky Mountain stocks them.

One thing you must do is check the oil pump. If any shards of bearing got in there it will have scored the pump surface and you will nee to replace that as well.

Kind of important as oil pressure will be reduced. The manual tells you how to check it.

I agree with a previous poster in that this bike most likely has a few more than just the 30 hours the previous owner claimed. I'm on my 6th Yamaha 4 stroke since their inception and the reliability is legendary even when hammered and and not maintained properly.

Good thing you found the problem. Hopefully that'll be it for your problems and you can go out and enjoy the bike.

John

I tore mine down completely looking for a bad crank bearing after just 2 hours and wouldn't you know it turned out to be that dastardly skidplate.

After putting the thing back together, I cursed this darned thread.

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