Cam Journal marks on 04 RMZ250

[BENT]

I noticed these marks in the intake cam journal on the head and the cap. Its the roller bearing end and the bearing has a few marks too. I dont feel anything with my finger nail on them so I'm not sure if they should be a concern.
Any professional opinions on these?

 

[Rich Rohrich]

All the RMZ 250s do that. The cam may LOOK solid but it's flexing like mad at high rpm and it causes the end bearing to bounce around in the cap. As long as the bearing isn't bad, and the groove in the cam cap that positions the bearing (the retainer groove) isn't torn up, it's not a big issue.

 

[BENT]

Thanks Rich, I appreciate your opinion. I have an intake valve that is getting tight every few hours of riding, I went from a 2.9 shim to a 2.8, then 2.6 and its 0 clearance again. I plan on sending the head in to Eric Gorr to have the Kibblewhite valves installed, (I got them with the bike). Is it a great risk to try to get one more afternoon out of it?

 

[Rich Rohrich]

The RMZ/KXF 250s have a bad habit of breaking the valve heads off and trashing the cylinder heads after they zero out. Once the valve face is worn far enough to zero out the clearance it no longer hits the valve seat concentricly. Because the valve and seat are no longer meeting squarely it tends to bend the valve head back and forth each time the valve closes and the valve head can break off.

My personal opionion is not to risk it, but I've seen so many detroyed RMZ parts over the last 2 years that I tend to think conservatively when it comes to these engines as they wear.

 

[Jaybird]

Is the root of this a spring or wear issue?

 

[BENT]

Jaybird, I think its a wear issue, meaning if the spring were going bad (soft) the valve woud likely have excessive clearance and not close properly, I'm guessing either the face of the valve or the seat is wearing or both. Rich could tell us better, mine is speculation.

Rich, Thanks again for your replys, they are much appreciated.

 

[Rich Rohrich]

It's a combination of a 3 dollar valve spring made of defect laden steel that sacks out quickly and the hard coating on the face of the valve wearing off. The face of the valve cups and closes up the clearance. Once the hard face coating is gone it's just soft titanium running against a hard steel valve seat, and the titanium gets beat up quickly. Reshimming will bring back the clearance but the valve face is destroyed already so it will lose the clearance again in short order.