YZ450 cam journal scarring

[brycewchilds]

So I went to adjust the valves on my 04 yz 450 today and I found that the two intake valves furthest from the cam sprocket were so tight that I couldn't get my smallest feeler guage in. I took the intake cam off and find scarring on the cam journals. The metal has mushroomed over the buckets so I can't remove them. The bike doesn't have a lot of hours on it and has always had regular maintenence oil changes etc. The fluids are always topped off. What might cause this? Who can fix the head? I've heard that overtorqueing the cam caps can cause this problem. Any experiences or advice?

[ForsheeMS]

I just worked on one a month or so ago that had the same problem. This one had overheated which caused the damage but it can be fixed. You have to machine just a little material off of the base of the cam cap, torque it down on the head, and then line bore it to get your clearance right again.

[250xxx]

Hello I also have an 04 with the same problem. Hasn't been hot.didn't run low on oil.It has pretty low hrs it has never been opened up before now so the cam caps should have been to factory tourque specs.would like to know what caused this before i fix it to happen again.

[brycewchilds]

So I found this company http://enginedynamics.com/index.html and spoke with a guy named Mike. He sees alot of Yamahas with this same problem, always on the intake side. According to him Yamaha has really tight clearences like .001"-.0015" between the cam and the journal. Most other manufactures run .003"-.004" with out problem. Another thing that causes it is over torqueing the cam caps which causes cam seizure. Any way the fix is fairly simple. $130 and he remachines the caps and journal to looser tolerences.

[BC3]

Had that problem On my 03, seems that the clearance is tight from the factory and extended high RPM operation can cause a failure (that was my case since I ride short track and buzz the motor) I took it to a guy in Petaluma CA. that deals with cylinder heads almost exclusively.....(Engine dynamics) Mike Crowther is his name. He said he has repaired hundreds of them both Honda and Yamaha....The repair was cheap and hasn't been a problem since....

http://www.enginedynamics.com/

[FinchFan194]

^^^^Damn thats bright and hard on my eyes.