Start with oil pressure(£6.78 i think) switch as Ricardo says,i swapped mine out at 25k miles. I had oil dripping fast!!This is a bitch to get to.
Clean up the engine area and go ride a few hundred miles.I did and mine looked like your engine only less oil so i changed my base gasket and found the studs that hold the cylinder on was corroded so the gasket was gone on mine. Another tell tale sign was that there was oil/crap in my coolant yet no coolant in my oil(my oil filter didn't have weavy pleats).
Any specs of oil/crap in ya expansion bottle?