Rear master cylinder piston question??

I have a 78kz650sr. The rear master cylinder failed. I opened it up to inspect it and now have a question about how it goes back together.
The piston has three ports on it and a wheel that seems to allow adjustment from full open to full closed. Putting it together is no problem but how should I adjust the piston wheel/ports?? I have attached pictures below. Please help. Thanks!

Anybody?

I think you have a picture of parts # 20 and 21 shown in this illustration in the kz650 manual on page 105 (G22)

www.kzrider.com/modules/ServiceManuals/K...Service%20Manual.pdf

Yes I know it is a master for the front brake but it works the same way

Yes it appears to be the same part#21 the piston, but it does not talk about the adjustable wheel that the primary cup presses against. The wheel at the end of the piston covers 3 port holes. You can move the wheel to open then or cover them closed. The manual does not state what to do. Did I miss something? I have read two manuals now with no information about that. When I opened it, it was set almost closed with the 3 ports just slightly opened. Since the master cylinder failed I'm not sure if that is the correct position for the piston wheel that covers the ports. I hope that makes since. I know how to assemble the parts in chronological order, just no mention of the adjustable wheel on the piston. I can't help but think if it is adjustable there a reason, yet the manual says nothing about it.. Do you know what to do? I hope you understand. Thanks

I may be wrong but I always assumed that the holes should be covered by the arms of that wheel

By looking at the pictures, it appears to me the arms will never really block the holes. The holes appear to be in the surface that is below the height of the arms, flow will be affected but not blocked off.
It's unclear by the pictures what would keep the assembled position from moving in use??
I'm about to tear into my M/C and am hoping to avoid surprises
I would probably re-assemble mine with the holes unobstructed, my thinking being how can you have to much brake fluid moving in a relatively small area
Highly open for some knowledgeable tidbits

I've never seen one come apart that had the holes uncovered from the factory...Honda, Kawasaki, Yamaha, Suzuki...probably close to 30 that I've taken apart.

Also, the reed valve - ish part made of spring steel shouldn't turn easily...it should stay put.

Cover the holes is my vote, but it isn't meant to seal them off completely. More like a one-way check valve...not adjustable...same goes for the design of the cup seal...it lets fluid pass on the back stroke, then seals again going forward...