Its from letting your bike cooldown outside while its really cold. I live in Washington State and I ride almost year round. I store my bike inside at night, but its outside from when I leave in the morning till I take it in at night after im done going places. After the Primary Change iv decided to deal with the fact that my house is going to smell like motorcycle and my motorcycle will last longer. Ill let my bike cooldown inside from now on.
My primary got changed 1,700 miles ago, I planned on changing it at 1,500 but had a long ride day before yesterday. It was wierd tho, the primary oil was just a bit milkey but the inspection plate had like cream colored sludge built up on the inside of it, took me a while to clean it up. Makes me worry about the places I cant see. So like I said Ill be changing it in 1k just in hopes it cleans the rest out.