I have an Arai Quantum/f, it has the older removal mechanism which has a lever on each side of the face shield. I tried to remove it by pushing them up but somehow they came off, and now the face shield is stuck...

Looking for pointers to get it off and put it back together w/out breaking anything, please help!

 

I have the same helmet. When I first tried replacing the face shield with a smoked shield, I had the same issue. You really have to put some muscle into to get the shield out once you push the levers. I was afraid I was going to break something but it's okay to use some force- just make sure both sides are completely disengaged.