[SpudRider]

The space behind the headlight is well protected by the windshield and the bike's frame. I wash my bike with a garden hose, and I don't get any water in the headlight. Most dirt bike headlights are open in the back. In fact, the headlights of my other 4 motorcycles are open in the back, and I have never had a water problem with any of them.

However, if you are uncomfortable with the mod, don't do it. You should know that I did see some bubbling/distortion of the top of the plastic reflector after using the H4 bulb without a ventilation hole.