Everytime I change the oil on my SR I remove the mesh screen in the bottom of the oil tank in the front of the frame and clean it and I remove the sump plate under the motor and clean that mesh screen as well The screen in the sump plate is where you will generally find any metal shavings or broken pieces If the motor has had new cam chain guides fitted you might find aluminium shavings in the screen in the sump plate during the first couple of oil changes, I believe this is normal Once the cam chain has had time to bed into the new cam chain guides, say by the third oils change after replacing the cam chain guides, you will most likely see the screen is clear of shavings