CO2 Check Valve

Hello - I have a Korallin 1502 that has a brass check valve. Like many, its not working. I read you can take them apart and remove/replace the o ring.

Anyone know how to get the brass section apart? Doesn't look like it comes apart but I had read another thread in this forum that it can be done.

I've removed the plastic ends and see the spring/flap etc. Just don't know how to remove them from the brass sleeve.

(I'll be replacing it with plastic, but I need it operational now and I'll have to order one. With T-day approaching I'm a week out from getting one shipped without paying $35.00 for shipping)