I have had several unsuccessful attempts in creating one, using my own dimensions but similar design.
a (part file) in Solidworks of the motocross Helmet would be alot of help .
attached are some rough attempts in Modelling a Motocross Helmet.
I have had a look at you model. You might try to use the shell tool to remove the inside of the helmet rather than a revolve cut. Remember to select the faces you want there to be holes.
good luck with your model.