Cam journal wear

[L.Hughes]

I’m tearing down for a new piston right now in my 2013 YZ450. Just popped the cams out and I’ve got a bit of wear going on, both on the head, and cam tower. Also, only on exhaust side- intake has a little wear but totally runnable. The cams themselves look fine. Scratches are just deep enough to catch a fingernail. What are your opinions?

 

[AZ800]

The bottom pic of the cap is the only one that looks like wear.
Mic it and see if you have an issue or not.

 

[L.Hughes]

The cap definitely looks the worst. Unfortunately I don’t have tools accurate enough for any of those readings. Might need to take the head in??

 

[RACINSTATION]

I would see if a repair shop can polish up the head where the journal wear is. It looks fairly bad. I would replace the buckets. You don't want one breaking and that light circle on the worst one is right where it will break.

 

[M5-]

How many hours on that motor since new. Are you the original owner.

M5

 

[boondocker97]

I agree that cap looks fairly bad. A few common things can cause cam journal issues: low oil pressure, partially blocked passage, or overtightening the cap. In some of the older KTM motors the tolerances were so tight that anything over factory spec on the bolts was asking for serious trouble.

 

[L.Hughes]

I’m not the original owner, and I don’t know too much about it’s previous life. I bought it at the beginning of last season, threw a track on and put some pretty good hours on ‘er. I just wanted the reassurance of a fresh top end this year.

Any recommendations for a reputable shop in the NW?

 

[L.Hughes]

I agree that cap looks fairly bad. A few common things can cause cam journal issues: low oil pressure, partially blocked passage, or overtightening the cap. In some of the older KTM motors the tolerances were so tight that anything over factory spec on the bolts was asking for serious trouble.

I’ve heard some of those KTM’s actually had torque specs that caused the caps to be too tight! I’m always sure to use torque specs and a good wrench. I’ll have to do a little more digging to rule out lubrication.

Either way I think I’ll get her milled down and cleaned up- no point in going back together like this and seizing a cam mid-season!

 

[Revv Up]

Did you have any upside down run time? May cause the top end to starve for oil.