Hi,

I recently refurbished my in-laws' ca. 1982 LP Professional - new seals, thermal fuse, thorough cleaning - and more recently still performed the water-heated grouphead modification with the stopper and the small hole in the dipper tube. I am completely new to espresso and have learned all I know so far (not much!) on this forum.

The problem: I can't make a good coffee and I'm running out of things to try! I'd be so grateful for any pointers. Here is the data/setup:

-Ca. 1982 LP Professional with new seals and water-heated grouphead mod (IMS shower screen)
-1.1-1.2 bar boiler pressure
-Baratza Vario-W+ (2022 steel burrs) grinding between 2M and 3F (anyone else using this grinder?)
-Medium-roast coffees from Central America (Guatemala and Ecuador) primarily, within 3 weeks of roasting
-13.5gm doses with the original double basket, aiming for 26-28ml shots
-15-20 seconds of pre-infusion (rarely see any drips)
-20-25 second pulls after pre-infusion
-90-95 C on the grouphead temp strip (positioned at the front of the bell)

The shots I am getting are sharp and unpleasant, acidic, occasionally with undertones of espresso. There is very little crema. I'd guess they're under-extracted but I don't know enough to know for sure. Pulls vary between squishy and brief to extremely firm. There is always one small dent in the top of the puck near the water inlet but otherwise pucks usually seem OK.

One note is that the behavior of the machine changed notably when I did the water heated grouphead modification - the pulls now are squishier whereas before they tended to be very firm, and resistance starts much later in the pull - around horizontal. But there is still a lot of variability without changing any variables that I notice. Shot volume has also decreased - used to be around 33g max and now it's around 27g max. But the taste of the coffee hasn't changed with all of that.

Help! I've only been working with this machine for about 6 weeks but I'm losing faith. What else should I do?

1,2 bar is pretty high, for an LPP; de grouphead overheats very fast without thermal isolation.
I'm running mine on 1,4 bar, but I'm using the Bong isolator.
Before it was 0,7 bar, to prevent overheating.

How fresh are your beans?

Forget the shot time; my shots often take a minute orso.
Taste is the most important factor.

My advise for now would be to grind finer and don't care about the time.
Pre infusion around 2 bar, until you see drops.
Leave it standing to completely soak the puck.
Start the pull and aim for a 1:2 ratio.

If still too sour, grind finer, until it gets too bitter.
If that does not happen, but pulling a shot is becoming a workout, grind a bit coarser and extend the pull to 1:2,5 ratio or whatever yoy like.
Bitter/sweet comes at the end of the shot, that's why.

Good luck.

+1 on Guido's comments with a side of distribution,
A good WDT before tamping helped a lot for me in getting rid of sharp acidity that didn't disappear when grinding finer and finer.
Cheers,
Rob

Sounds like maybe channeling. You might already be too fine. My advice would be to grind way coarser then you think, then bring it finer until you get the time back up to 25-30. Pre-infuse for 5-10.

WDT for sure.

Not sure if you have a bottomless portafilter, but that can help diagnose issues.

I'd try pulling a bit cooler, 85-90C

If you don't have temp strips for the group head or a thermometer to take temp it is very hard to get a good shot. $8 goes a long way to ending frustration with a Pavoni.

Sounds like your group is too hot when pulling those beans, 85 range.. As far as crema the lighter the roast the less crema you get. Same with high pressure pulls, less crema the harder you work. Aim for a nice slow pull just at resistance. Should feel like cutting cold butter.

Pavoni's also tend to want a finer grind than any pump for a similar flow rate. See if you can get the grind fine enough to choke it, then dial it coarser to get a good feeling pull.