By Josh Andrews (Josh_) on Thursday, May 4, 2000 - 10:56 pm:

Blast oil cap
Shades of black/grey from bottom to top:
Frame, Tank Cover, Grommet, Lip of oil spigot, Dipstick
Make sure that lip is showing, or you'll have a $4500 smoke machine ;)

Arrows left to right:
Tank Cover, Grommet, *Oil Spigot Lip*, Threads From Dipstick, Dipstick
The threads are seen as the cap is backed out.
If you don't see 1/8" or so of lip, you'll leak oil as the grommet isn't fully seated, or is upside-down.
Josh