Hi,

I'm nearly done refurbishing a 1990 Astoria lever, but had a quick question and was hoping someone could help. In putting the groups back together I noticed that when the the piston is raised, it's not clearing the holes in the group sleeve where the water enters the chamber. I've measured it, and it's 1/16th inch away from going about the holes, so it is below the gaskets on the piston, but hitting the very bottom of the piston.

Anyhow, I was just wondering if anybody knew if this is not supposed to be the case, if the piston is supposed to clear the holes, or if its no problem at all! Any insight would be great.

Thank you,

Jason

Check that your piston is screwed fully onto the piston shaft.
If you haven't given the inner threaded hole of the brass piston a careful cleaning it may not allow you to get the extra 1/16 of an inch you need.

Something else to check; are the holes of the inner sleeve open and not clogged?

I can't think of anything else.

Clint and Flint (Astoria owners), any suggestions?

The shaft not being fully screwed into the piston at the bottom and into the cam support piece on top are the only things that comes to mind for the mentioned problem.
They both need to be fully screwed in, on my machine at least.

I suspect that this is a deliberate part of the design, that would be like the La Pavoni lever groups. The La Pavoni lever groups are deliberately like this. The idea is supposed to be to have the incoming water run down the side of the cylinder wall instead of spraying around which would disturb the puck. It also reduces the time until the coffee puck is completely covered to enable air trapped below the piston to have time to be driven out by the water's vapour pressure. Of course the water entry place must be below the piston seals or water will be unable to enter at all. As has been pointed out this can happen when the piston is not tightened all the way down.

I'll check the shaft to make sure its totally in the piston and the group fork, but I screwed them in like crazy.

It seems that this might be the design though because it's pretty spot on with the clearance. It's just set right at the bottom lip of the piston, it would make sense if that were the design. I'll check when I get home though.

The cylinder seals themselves are different thicknesses. Using the wrong size o ring in the lower position on the cylinder could throw off the geometry.

Hi Doug,

I'm pretty sure I bought and used the right sized gaskets - I got them from Nuova Ricambi and ordered according the the diagrams. However, are you saying that there should be nothing at the same level as the holes in the group sleeve?

I've never actually looked up into the sleeve with the piston raised on my Astoria. Doug's right though that the two o-rings that seal the sleeve to the cylinder are different sizes. I remember he clearly marked them when I bought them from him.

If you changed a spring, sometimes it's really difficult to get the piston rod threaded all the way back into the top knuckle. Maybe just try pulling a shot. If it operates properly, it's probably assembled correctly.

I am going to digress a little:

actually from memory: on the La Pavoni the hole never clears the piston- it is above the seal. But the water can travel past the seal- down and alongside the downward pointed V. Once the chamber fills and becomes pressurised the v walls are forced out and against the walls making a seal and stopping more water being forced in. I seem to recall being quite surprised when I discovered this... I could be wrong- it has been a while now since I last tinkered with a Pavoni and memory will play tricks...

It seems to me that this design is intended to help the water cool a little more as it enters the piston chamber. I recently noticed that the (so called) Bosco group uses 4 water inlet holes spaced all the way around the piston wall. My Faema lambro group has only two holes placed side by side in the normal position opposite the group neck...

I figure the Bosco design is also intended to fill the chamber more evenly and dissipate the heat better to the cylinder walls... I saw a video of it in action on youtube but now cannot find it....

I have been thinking about heat dissipation in manual groups- I wonder how much of it goes up through the piston head into the shaft? Perhaps adding a longer piston shaft to machine like the pavoni could help them shed heat from shot to shot...

Having said all of that it probably has nothing to do with your issue or machine...

Actually the main reason to have water enter along side the piston is so that as much water vapour forms as possible as it first begins to enter the chamber so it can drive the air that gets drawn into the space as the piston is raised. It also decreases turbulance which can disturb the puck, even with the screen above it. It also slows the entry of water, which also decreases turbulance and gives more time for the air to exit before the puck is covered completely with water.