Join Date: Feb 2004
Location: Rocklin, CA, USA
EMS shims are made from A2 tool steel and are hardened through, so sanding them down to size will not affect the hardness.
Ducati OEM shims are not as hard, but not sure what heat treat process they have been through. I would say that its ok to sand down OEM shims cause the surface contact area is very large (on the bottom of the shim for closers). The high stress areas on the shim are in the groove where the half rings sit, not on the bottom of the shim. Also the closer shims do not see the wear on the bottom since the rocker arm is simply pushing upward on them. Not like the cam and rocker where you have a sweeping motion and the wear would be much more. I have known people to machine down the OEM shims and they still worked fine.
Concerning cost, we all know ducati charges alot for their parts. How come car belts are so cheap, but Ducati belts are big bucks. Can you say big mark-up? No different for shims.
To remove .015 in. from a shim would take a very long time and your arm would get tired. A few thousanths is no problem.