HOW TO CHANGE YOUR Z-1 LENS
Start by taking the visor off of your helmet using a quarter on the outside and a half-inch wrench on the inside. The original black plastic bolt is a quarter-turn locking mechanism, so pay attention to how it works. It locks in one position and releases in another. You'll have to pop it off the first time.
Next, take the old lens off. DO NOT REMOVE THE TAPE OR THE PROTECTIVE COVERINGS ON YOUR NEW LENS EXCEPT NEAR THE HOLES IN THE FRONT AND BACK.
Now,install the new lens and visor on the helmet (the lens should move independently), but do not tighten the bolts.
Next, remove the tape and the protective film on the front side and adhere it to the visor from the center out (this allows equal stress across the lens).
Finally, tighten the bolts and remove the protective film from the back of the new lens. That's it. You're done.