OK, so I took apart the forks on my '97 YZ250 to replace the oil seals. I bought new oil seals, dust seals, and shock oil. I can put everything back together but I need help with the shock oil. I tried to drain as much as I could without taking apart the lower section where the oil is stored. When I go to put the new oil in, how do I know when it's full? How do I know if I have enough oil in there? I think I got all of the old oil out, but what if not all the oil is gone.