I take my vents (the black sliding part) off during the summer. It's so much cooler on my legs anyway and keeps the comfort of the lowers.

 

Iike I said in another post if you look directly from the front of the bike
toward the engine it looks like more air will be directed right at that
front cylinder with those vents (closed)
When they're opened the air will just rush PAST them and hit your legs.
I'm actually going to cut those little tabs off as I believe that will allow
even more air to hit that front cyclinder. I don't know...

I think the OP should take some temp readings with the vents closed
just for ***** and giggles. We may learn more about these air flows
around the engine!
Ive read that the lowers were designed to direct air toward the engine
and I do believe they really do.
I'll see if I can borrow this electric temp sensor from work and
do some tests also.

Thanks for reading!
Pete

 

Bump? lol

 

I take my lowers off in warmer weather. I run an oil cooler and dash mounted oil temp gauge.I have the vented lowers and run them open in warm weather ,but they run 20 -30 degrees hotter with them on.

 

In St. Louis wednesday temps in mid 80's- lowers on- my oil temp never got much higher than 180's by in-dash temp gauge.

 

I read about this in a HQ blog article, tried taking mine off last summer it does make a big diff. here is article.

installed lower fairings on my FLH over the winter and have been riding with them on up until yesterday. It's bouncing close to 100F here in Atlanta, so needless to say, it's been a little warm. Over the past few weeks I've been doing some tuning, building maps, etc and of course I like to always keep track of cylinder head temperatures. I found what I expected on the front, just below 300 deg at the spark plug...perfect. Then I checked the rear...375F! Yikes...that's a bit too hot for my taste. I of course played with fuel mixtures and timing and nothing seemed to make a sizeable difference until I took the lowers off (with are "vented"). I was expecting it to lower temps a little but not 70F lower! Just an FYI.... Happy Motoring!

Kevin