Good morning,
I have a Zacconi Riviera espresso machine about 15 years old. Recently the shower screen is popping off after I've made an espresso. Excuse my terminology, it seems the piston in the group head is pushing it off as it ends its function squeezing water through the filter. Is there a way to adjust how far the piston comes down to meet the screen? Or do I need to bend? Tighten the shower to fit very tightly again the mount in the group head?

Thanks for your help with this. Wonderful reliable machine it is!
Timothy Gee

There should be a nut on top of the piston rod that limits the travel of the piston. Check to see if the bottom of the piston does actually protrude.

You can also tighten the ridge on the shower screen. I have heard that the screen can bow a bit, which leads to a looser grip. Be careful as these may not be the easiest to replace..

Is it possible the nut at the top of the piston rod has come a bit loose? That could allow the piston to go too low at the end of its stroke.

Unfortunately I don't have that nut at the top of the piston arm to adjust the piston length. My model has a spring in the group head and the lever rests in the up position. The piston extends below the shower attachment edge 1-2 mm.
I'll try bending the shower edges in just a twitch and see if that works.
If that doesn't work, can the piston arm be adjusted to shorten its throw just a bit other than the nonexistent nut atop the piston arm?

Another possibility is the connection of the piston to the piston rod. Maybe the piston is not fully tightened on the rod?

If I elect to dismantle the piston and piston arm from the group head, do you have any sage advice or tricks as
I approach this challenge? After the shower popped off but again, I tried hand tightening the piston from below, but it won't move.
Thanks much for your replies. TG

Spring-driven Zacconi Riviera, Elektra gaskets and restoration

He had a similar issue, which turned out to be a missing roller bushing on one of the lever pins. Disassembly of the spring piston often requires some sort of tool to preload the spring to remove the lever and allow you to gradually release the tension to get the piston out.