Big oil leak

My ride is a 2007 GRiSO 1100.

My problem began when oil pressure light went on. There was plenty of oil, so it was probably the oil pressure sending unit. After a week and little bit, the part comes in, I replace the unit, and the light stays off. But I have acquired a rather large oil leak and I'm wondering where I went wrong. I did find a small washer on the garage floor, and I don't know if it belongs somewhere on the bike.

I also had to replace the head temperature sensor. While I was doing this, I had to remove the left hand oil line, and the washer could have come from there.

Any help would be appreciated.

Can you see where the oil is coming from? You have two sources you've touched, check them. Yes, both the oil feed to the head and the pressure sensor use aluminium sealing washers.

Pete