if your filter is properly oiled (has to be a K&N type filter - the SE filter elements aren't oiled) then it shouldn't really matter much but you dont want water getting into your motor so to be on the safe side some people prefer to have it covered in the rain.........personal preference I think........most old timey bikers I've asked scoff at covering it - they've all told me not to worry about it but I still do............

 

Below is a copy of a post from this last August. An open filter can handle a lot of rain, but...

I've seen several posts about exposed air filters not having a problem in rain, and earlier this year I got pretty wet in the Seattle area one night with no problem. But let me tell ya...

I just returned from a 4 day jaunt. Day two was going from Lewiston, ID to Missoula, MT over Lolo pass. It just so happened that the day we rode this leg was on the very day that a record 2.2" of rain fell on Missoula. We were in the rain for the first hour, then cleared for an hour or so then rained hard the rest of the way in.

The bike ran fine until the last 30-40 miles. It started stumbling, rough acceleration, etc. I thought it was going to die a couple of times, but it got me into Missoula. I even tried riding with my right leg over the filter to protect it a bit, but it didn't help. The next morning I noticed the usual reddish/pink K&N oil was all gone off the filter - nothing but white. When I got it recharged there was still water in the intake, and what's worse, small deposits of fine dirt.

I will be buying a rain sock on Monday. May never need it again, but I'll have it with me on every trip.

I did buy one, and will keep it with me...

Steve

 

Better be careful than sorry later