Trying to start!

Thought I had better see if it would start and run. Drained oil as it had not been started for a number of years. Not a lot came out so filled with fresh. No oil in gearbox either so filled that. Plugs checked and in good nick. Battery had been on charge and was good. Not a lot of fuel in the tank so put a splash in. Try as I might, couldn't start her. Got fed up and left it for a few days. Then realised that maybe I should have drained and replaced the fuel. Old stuff looked like Tizer! Hey presto, she runs. Rough as heck and only on full throttle and for some bizarre reason the brake light flashes of its own accord! Had issues with the Amals on my last Norton so was aware of the issues with blocked pilot circuits. Borrowed a sonic cleaning bath from a clock making friend. Stripped and cleaned including a good poke with a teeny tiny drill bit. Re-built with service kit from AN and runs and idles lovely now. The flashing brake light was a knackered switch that was shaking on and off with the vibration. New one fitted and sorted. However when running I could hear what sounded like a something rattling around in the primary case. investigated and found the primary chain was so slack is was wearing a groove in the top of the case! There wasn't any oil in there either. Tightened and new oil added. Sorted! A question for you. When the oil went into the oil tank it was new fresh and clean. After starting, checked level which was good and appears to have a return flow although its a bit spitty. But, the oil now appears to milky. On closer inspection it has been aerated. Is this normal?