Replaced the O'Reilly hydraulic clutch assembly again. This unit lasted less than seven months.
Things to watch out for:
Flange gasket on master to firewall doesn't keep any water out. Might as well be an open hole to let rain in. This time I used Permatex 80016 Non-Hardening Form-A-Gasket No. 2 before installing. Last time I used a rope of Scotch (3M) Removable Mounting Putty - White to seal it off after I discovered the leak. Note: this also works for anything else on firewall leaking, like the electrical connector.

All fasteners are 13mm, not 1/2". Using a 1/2" socket on the slave cylinder made for some annoying times.

New master cylinder rod went onto pedal peg pretty tight, rough going. And you can orient that thing wrong. The barb on the plastic should face away from the pedal. If you lose the factory metal clip, I'm pretty sure the easiest solution is a paper clip run through past the first bend. Otherwise, Harbor Freight has a hitch clip assortment with sizes that fit, also could use a cotter pin.

This got replaced because the master was leaking fluid down the rod and into the cabin, also because the flange gasket doesn't seal out any water.

Also note, the slave cylinder is prone to disassemble itself on removal. If you are pulling it from the fork for any reason, might as well order a new one.

The upper stud on the slave cylinder came out, rather than the nut coming off. Couldn't get the nut off so reinstalled it like a bolt.

Does anybody know the size of the slave cylinder mounting studs? The ones here are definitely not what I have. Mine are 13 schmillimeter (I think that is M8?)

 

I stand corrected. Those studs are 5/16-18 on both ends and a 13mm socket fits on the proper nut (1/2" hex). Ace doesn't have any, so looking around a bit before I order some.