Any ideas how to make them less humid, mine are very foggy after almoust every trip.

[2015 Z Force 800 53/Trail EPS]

Move the vents away from the radiator.  The farther the better.

I haven't had that problem but I've thought that if I did I'd tee the vent lines into one and run it to the airbox and connect it to that box with a barb fitting. The airbox interior (outside of the filter) will be a very slight bit lower pressure, and there ought to be a constant leakage of lesser humid outside air into the headlight fixture, resulting in that condensation being purged whenever the motor is operating. 

If the headlight fixture proves too airtight a seal then a tiny hole might be needed.

[2015 Z Force 800 53/Trail EPS]

The fixtures are well sealed with the vents being the only access for ventilation and pressure/vacuum relief. Running the headlights heats up the air inside as well as the case. Then when you hit water and splash up on them, it rapidly cools the case contracting the air and pulling in air through the tube. While it's doing that the water you hit also splashed on the radiator and made some steam and is blasted out the back because of your forward movement..right at the tube's ends.. where it gets pulled in. With no where to go it just condenses on the interior until it finally drys some weeks later sometimes. So...don't use the headlights..or move the vent tubes away from any possibility of getting anything but ambient humidity. Remember though that whole area past the radiator under the plastics can hold steam so the tube ends need to be before it...like just inside the grill and as low as possible.  Some areas may naturally have too much humidity and will fog anyway...and for that I say for sure do what Glenlivet says and make another vent hole because I don't know of anyone else that seals their headlight units so tight they need vent tubes like CFM...and no one else seems to have this problem.  I don't have the problem because..I don't use the headlights and...I don't have any water to splash through...lol