Condition of Valve Shim

[beRto]

Hello All,

I recently checked the valve clearances on my 1995 GS500E and found that one was a little tight.  I got a used replacement shim and found that it had some minor surface damage on one of the sides.  I installed the shim with the damaged side down.

Do you think this is ok?  Should I get another shim?

thanks.

[dgyver]

What kind of damage? If it is just wear, no problem . If it is a chip or crack, replace it.

[beRto]

Not chipped or cracked.

The damaged looked almost like surface rust.  I tried to scrape it off with my fingernails, but no luck.  Further inspection revealed that it was not anything on the surface, but rather the surface itself was a little pitted.

My only worry is that it will continue to wear and send filings into the engine.  I figure this is low risk because I installed the damaged side down.  For the same reason, I don't expect any harm to my camshaft.

[GeeP]

Like this?

[beRto]

I'm not sure what's showing in the white boxes (hard to see); it looks like the entire surface of the shim is damaged?  If so, I had a small section that looked like that (~2mm diameter circle) just off-centre.

thanks.

[GeeP]

This is a lifter, probably from a Lycoming O-320 H2AD aircraft engine.  The surface disfigurement is called spalling, and is generally due to lack of sufficient lubrication at the cam/lifter interface, rust on the lifter or cam lobe face, or very high time.

You'll be fine by turning the shim over.  I just thought I'd post a photo to help you identify what was going on.  Usually, spalling will begin at the center of the shim/lifter and work out.  This is because the center of the shim/lifter is almost constantly in contact with the cam, whereas the outside of the shim sees contact only once a revolution.

The white boxes show where the lifter was taking an eccentric path around the cam lobe due to wear in the lifter bore.  Notice how the margin thickness changes?  This really doesn't concern us though.