I've had my Silvia for almost 7 years, but the past 4 years I've had difficulty pulling a good shot. I think something happened when I adjusted the OPV at one point and it was all downhill from there.

I am absolutely unable to choke the machine with a fine grind. Thinking I had a grinder problem, I've been through a Rancilio Rocky, 2x Baratza Vario's and a Breville Smart grinder.

The grinders are adjusted to where the burrs are touching. As fine as I can go, but with 18g espresso in a 17g VST basket I am getting over 50 grams of liquid out in less than 20 seconds. I used to be able to choke my machine if I went too fine with my Rocky, but not anymore.

So I've been adjusting the OPV valve and I experience the same result when set to anywhere from 10 to 5 bar pressure.
I've been calibrating using the graph here: http://www.schneordesign.com/Avi/Silvia ... ilvia1.htm
And the one from this forum shown at the bottom of this post.

But nothing I do changes it. I haven't pulled many shots on this machine in its lifetime, but it's been taken care of. Only filtered water and our water is very soft here. Cleaned regularly. I've never changed any gaskets or washers, but I have no leaks or problems with the seal.

Help! What should I try.

How fresh are the beans?
Are you clearing the screen with the coffee? Do you pass the coin test?

How is the flow at the start? During the first moments when you turn the pump on, how long before coffee comes out? The first 4 or 5 seconds nothing should come out and you should hear the pump ramping up to the 9 bar. If coffee just starts flowing within 1-2 seconds of turning the pump on, it is not a problem with the OPV, it's the puck that is not offering enough resistance.

How do you know you can't grind any finer? Can you leave your fingerprints behind if you press down with your finger on the grinds?

So are you saying you USED to pull good shots on this same machine? If so, what changed?

I've only been using my machine about 4 months now, but I went through a short learning curve to get rid of gushers.

1. Make sure you have a fine enough grind. Choke the machine then loosen the grinder a notch or so (or however you adjust the fineness of your grind)
2. Gently tap the portafilter on a tamping pad to settle the grounds. I tap about 5-6 times. This helps minimize any pockets that create fissures that cause channeling
3. Press straight down with the tamper. Do not twist and and attempt to polish the top. This can crack the tamped grounds.
4. DO NOT tap the portafilter or bang it ever so slightly AFTER tamping
5. Make sure that the portafilter is cranked all the way to the right (close to the red dot on the grouphead). It doesn't have to make it all the way to the red dot.
6. Lastly, what's your cleaning procedure when finished? I take a toothbrush and clean the remaining spent grains off the shower screen while running some hot water through. I catch the droppings in a small plastic tub. Then I use the small round blind filter (rubber disk with handle) and place it in the portafilter. I mount the portafilter in the grouphead and turn on the water. As the water flows, I loosen the portafilter partially so that excess water flushes out the sides. This washes away any grinds that may be on the seals causing the filter basket to not seal properly in the grouphead. That's it! Ready for next use.

If everything is right, you should get espresso flowing at about 5 seconds and have enough volume at 25-27 seconds.

A common mistake/problem with Silvia is using too much coffee. Wipe the screen dry and lock the prepared portafilter in place, then carefully remove it before attempting to brew. Are there any marks on the portafilter or is the coffee disturbed? And as illogical as it may sound, try going to a coarser grind and working back. And don't be afraid to tamp like a WWE wrestler, so long as it is level. Grunt if you like. And has been said, stale coffee is a definite cause of gushers.

Thanks for the feedback.

I've been unable to choke the machine. The grinder will make some pretty awful sounds and it still wont choke my Silvia. The coffee bunches up when pressed between my fingers just as expected. I used to pull some great shots and could calibrate the first shot (my recipe is 17:30g at 28 seconds) almost perfectly by the feel of the grounds alone.

At 18g it can touch the shower screen due to the grounds expanding with the water. At 17g it's perfect, but also produces the same gusher of a shot.

I've tried with coffee anywhere from 1 to 12 days old. Blue bottle, Intelligentsia, or a local roaster that I'm fond of. Today's test is 4 day old roast. I've learned that about 7 days is peak for my tastes even though the shots aren't as visually appealing. Tamp is 30lbs as measured by a scale. I've got the tamp down. I've become insanely picky of all other variables in trying to overcome this problem. I have VST baskets, I do the WDT, everything is weighed, no banging the portafilter. Cleaned with a grouphead brush and wiped down after each shot. Backflush after each session. The rubber gasket is in perfect condition from what I can tell. No leaks with a blank filter in place. Monthly the screen gets taken off and the grouphead cleaned.

I'm pretty certain it's the machine where something has gone wrong because I've changed everything else, but I'm not sure what to check. I will try with coarser grinding next time I have the patience. It seems counter-intuitive, but I'll try most things by now.

It seems to me that the next variable to quantify it the brew pressure. Either putting together a PF pressure gauge or installing one temporarily or permanently in the Silvia. Maybe have another HB'er or home enthusiast come over with their coffee and their grinder to try.

Yeah, where are you located?

Perhaps someone is close and has a Silvia and can walk you through it.

Also, it seems like you've adjusted the over pressure valve. Chances are it's now too high too.

Get this pressure gauge to screw into your portafilter!

http://www.espressocare.com/products/it ... sure-gauge

I'm near Vancouver, Canada.

That's what I thought the problem was, so I have it adjusted so low that when I turn on the steamer, it starts shooting hot water out the OPV when it starts to reach boiling temperature. Based on the flow rate, I estimate it to be 4-5 bar pressure. Really strange. Any benefits from the gauge over using the graphs?

From simple physic standpoint, there is absolutely no way that a machine can't choke with fine enough grind, regardless of pressure (anywhere from 0-30 bar). Can you imagine the Silvia punches through a blind filter? Nope. That's exactly what the fine coffee grounds are - a solid resistance, when they're ground fine enough.

Problem lies in the grinder or the coffee, definitely. I will bet my one week of espresso on this. Either the grinder can't get fine enough or the coffee is not fresh/too light roasted(creating not sufficient fines). Don't chase the brew pressure/OPV until you can choke the machine. Borrow a more solid grinder.

Also, just read that you're using a VST basket. Those require really really fine ground. You have the stock basket around? Dose that 14-16g at finest setting and pull a shot.

The gauge adapter will give you actual pressure (for your particular unit) versus interpolating from a graph and assuming the pump and valve are set correctly.