I would not put the brake line in anything but brake fluid. Brake fluid is easily contaminated, and does turn brown when old. I would just flush it good with clean brake fluid, if it is not plugged up you should be good to go.
On the chain, if it is a O-ring chain, you do not want to soak it in anything, 90 wt may cause the 0-rings to detereoate.
ATCnut
82 185s - sold
83 200x (hopped up)
84 200x (stock)
84 70 (lost this one to the DMV)
85 70 (soon to have lights, a foot brake, and CDI ignition)
84 200es (parts trike) - sold
85 350X (the best)
85 350X (siezed motor, dream of a poweroll kit someday)
85 250sx (frame was trash, got parted out)
86 250sx (the tractor)
86 250sx (a nicer tractor)
86 250sx (an even nicer tractor)
87 200x (parts trike, its really rough, a dog was chewing on it for a while)
87 250es Big Red (the tank!!)