GEM FRONT BRAKE CYLINDER REBUILD.
Gem front wheel cylinders aren’t always available.
The existing cylinders can be rebuilt.
The existing Cylinder will have to be honed until there are no scratches or marks in the bore.
Dorman 351712 cylinder repair kit has the pistons and seals you need to replace the old parts.
These are an exact fit but require you to cut a groove in the shoe end. You can do this any number of ways. I wrap the piston in tape and clamp it lightly in my vice and use a die grinder.
Blow off the parts and put every thing together.
I bought the kits on Ebay for $17 each because Nevs was out of stock on cylinders. New cylinders are the way to go but if they arent available this is a viable alternative