Normally I tend not to sweat shot volume, but I recently finished putting back together a Zacconi Baby Lusso and the shot volume is tiny, like half an ounce if that. I'm no stranger to levers and thought that perhaps the volume would be more like a Europiccola, but it's nowhere close. I've tried pumping the lever a bit and I hear a squishing sound before the first drops come out.

Any ideas about why the volume is so low? I assume operator error, perhaps I installed the piston incorrectly (though I don't see how that's possible)?

Just a guess, but if the boiler pressure is below .8 bar it won't fill the group with as much vigor as would a higher pressure.

Maybe that's why they call it the baby...it makes baby shots???!!!!

Presumably you had 'full' volumes before your rebuild? At the very least you should get a lovely ristretto so not all bad news!

Assuming the p-stat as mentioned above is fine (you should be getting a good shower spray when the lever is at the top), are you feeling much resistance on the downstroke? Or is it quite springy?

Depending on what size basket you using, a gentle Fellini preinfusion technique will help to increase vols.

Failing all that, the culprit would be the piston head seals or the seal around the dispersion screen. This may mean new seals, or at least a clean and a lube with the current ones. Dont forget that you could have leakage between the inside of the seal and piston groove - something that cant see directly.

Good luck

Thanks for your responses, I had not used it prior to rebuild. Pressure is just over one bar. New seals are soft and lubed. I will note that the lever doesn't travel as far as a Europiccola. The downstroke is very springy and I do not feel much resistance.

I hear a squishing sound before the first drops come out.

Perhaps some water is getting around the seals and flowing back towards the boiler—do the seals fit quite snug around the piston? If not, OE has a method for shimming the piston.

Seals are snug. It really feels like there is air in the piston. The water is getting a little dirty too, so clearly pumping it is pushing water back into the boiler.

mikekarr wrote:The water is getting a little dirty too, so clearly pumping it is pushing water back into the boiler.

Bingo. If the water in your boiler is getting 'dirty' from coffee then generally that means the seals are not sealing properly. Espresso is escaping past the first seal on the downstroke (likely to be the problem seal your case), past the second seal (which is expected as it is 'facing' the other way - with its job sealing water above the piston, not from below) and the force of the downstroke pressure is bigger than the pressure coming from the boiler resulting in coffee finding its way into the boiler. No wonder you are finding it springy with little resistance.

I had a similar problem with my PV Lusso with a dirty boiler. It was that first seal that was the problem.

The trouble is that seals may seem fine to you to the naked eye, seated well and nicely lubed but often you cant easily what the problem is. You can get leak between the inside of the seal and the piston groove, or a tiny nick somewhere, or that the seal itself isn't perfectly snug. OE has a solution that helps fill the gap of the piston groove so that it fills the seal better. I think that is where you should be focusing on.

Fascinating, I will investigate this further. That's what I get for putting the tools away!

The baby is kindof weird in a way. It uses a w seal on the bottom and the specs call for a v seal on the top of the piston, as there is no rod seal. If you are having blowby the seal you could try taking them out and lubing the back side when you install it, or even trying a shim on the piston groove....teflon tape is a reasonable experimental approach that most people have. Adhesive high temp silicone tape is a nice permanent (ish) application. Usually a back lube with Dow 111 will seal it. We got a bunch of Zacconi seals and they don't send the v seal they just use 2 w seals on the Baby even though the schematic shows a w and v format. But then, there is the old baby and the new baby, or toddler and infant, and so things can get confusing.