Don't obstruct the vent hole, and if you have the cover off and looking at the guts, may as well verify that you have a CR or WR per David Kee's instructions.
"Gear ratio is determined by tooth count on second gear. If it has 28 teeth, it's a close ratio. If it has 31 teeth, it's a wide ratio."
You would be surprised how many guys think they have one when they really have the other.
