Right now ive got your attention .... ive got a new Enduro helmet never worn but the shell has gone all sticky Its almost like sticker glue but the whole helmet is covered ... ive tried white vinegar pledge polish and brake cleaner ... you can remove it with your nail then rub like fook with polish then in the end it will come good but what a pain in the arse ... So what you u lot recon ?
I had a caberg open face helmet and the same thing happened to it. Got it out of the bag and the outer surface was all tacky, wtf!
wd40 or baby wet wipes, possibly even something like tar cleaner from halfords. All will remove a gummy sap
Only used the brake cleaner on a inch square .... i only will use it for Enduro no road riding not binning it it not even got dirty !
So you like to play russian roulette.... Respect! Why not up the ante? Tape off two further inch squares. Treat one with battery acid, and the other with caustic soda.