When you get hot enough you will gladly stand under any suitable water source or jump in the nearest river wearing all your gear 
I find a wet hankerchief tied around your neck helps as does filling your boots, gloves and lid with water and riding with your visor up
There is no gear except the still suits racers wear that will keep you cool when it's really hot.

I find a wet hankerchief tied around your neck helps as does filling your boots, gloves and lid with water and riding with your visor up
There is no gear except the still suits racers wear that will keep you cool when it's really hot.